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2021 * ![Tags Icon](https://unit42.paloaltonetworks.com/wp-content/themes/unit42-v6/dist/images/icons/icon-category.svg) Categories: * [High Profile Threats](https://unit42.paloaltonetworks.com/category/top-cyberthreats/) * [Vulnerabilities](https://unit42.paloaltonetworks.com/category/vulnerabilities/) * ![Tags Icon](https://unit42.paloaltonetworks.com/wp-content/themes/unit42-v6/dist/images/icons/icon-tags-grey.svg) Tags: * [CVE-2021-26855](https://unit42.paloaltonetworks.com/tag/cve-2021-26855/) * [CVE-2021-26857](https://unit42.paloaltonetworks.com/tag/cve-2021-26857/) * [CVE-2021-26858](https://unit42.paloaltonetworks.com/tag/cve-2021-26858/) * [CVE-2021-27065](https://unit42.paloaltonetworks.com/tag/cve-2021-27065/) * [Exploits](https://unit42.paloaltonetworks.com/tag/exploits/) * [Microsoft Exchange Server](https://unit42.paloaltonetworks.com/tag/microsoft-exchange-server/) * [Zero-day](https://unit42.paloaltonetworks.com/tag/zero-day/) * [![Download 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[CVE-2021-26858](https://msrc.microsoft.com/update-guide/vulnerability/CVE-2021-26858) and [CVE-2021-27065](https://msrc.microsoft.com/update-guide/vulnerability/CVE-2021-27065). As a result of these vulnerabilities being exploited, adversaries can access Microsoft Exchange Servers and allow installation of additional tools to facilitate long-term access into victims' environments. There has also been a report of multiple threat actors leveraging these zero-day vulnerabilities, meaning post-exploitation activity may vary depending on the purpose of the different threat actors. These vulnerabilities affect the following Microsoft Exchange Server versions: * Microsoft Exchange 2013. * Microsoft Exchange 2016. * Microsoft Exchange 2019. Microsoft has released an emergency out-of-band [security update](https://techcommunity.microsoft.com/t5/exchange-team-blog/released-march-2021-exchange-server-security-updates/ba-p/2175901) to patch these vulnerabilities. We strongly advise immediately updating all Microsoft Exchange Servers to the latest available patched versions released by Microsoft. Due to the surge of this malicious activity, we've created this threat assessment for overall threat awareness. Full visualization of the techniques observed and their relevant courses of action can be viewed in the [Unit 42 ATOM Viewer](https://unit42.paloaltonetworks.com/atoms/). **If you think you may have been impacted, please email [crypsis-investigations@paloaltonetworks.com](mailto:crypsis-investigations@paloaltonetworks.com) or call 855.875.4631 to get in touch with the Crypsis Incident Response team.** ## Activity Overview: Exploits of Microsoft Exchange Server Vulnerabilities There have been reports of activity from several threat actors exploiting four zero-day vulnerabilities affecting Microsoft Exchange Servers. When these vulnerabilities are chained together, threat actors are able to exploit and gain access to Microsoft Exchange servers. For this attack to be successful, the adversary would first need to identify an on-premises Microsoft Exchange Server that is able to receive untrusted connections from an external source on port 443. If an adversary is successful in securing a connection, they can then exploit [CVE-2021-26855](https://msrc.microsoft.com/update-guide/vulnerability/CVE-2021-26855) to authenticate themselves as a Microsoft Exchange server. This can be followed by the exploitation of [CVE-2021-26857](https://msrc.microsoft.com/update-guide/vulnerability/CVE-2021-26857), [CVE-2021-26858](https://msrc.microsoft.com/update-guide/vulnerability/CVE-2021-26858) and [CVE-2021-27065](https://msrc.microsoft.com/update-guide/vulnerability/CVE-2021-27065) post-authentication, allowing the adversary to gain remote access. If access is achieved, the exploited vulnerabilities will allow threat actors to execute commands remotely, which can include uploading a [China Chopper webshell](https://attack.mitre.org/software/S0020/) to establish persistence in the compromised system. The webshell would then allow the adversary to steal data and execute additional malicious actions, such as downloading remote files or network service scanning. When the webshell is deployed, post-exploitation activity typically occurs in the system, most commonly the use of Procdump to dump Local Security Authority Subsystem Service (LSASS) process memory to obtain credentials. There have also been instances in which threat actors downloaded additional tools, such as Nishang and Powercat, to support their actions. Following the extraction of credentials and data from the compromised system, threat actors often use compression utilities such as 7zip or Winrar to compress and stage the stolen data for exfiltration. It's worth noting that since different groups have leveraged these vulnerabilities, post-exploitation activities may vary depending on the actor behind the attack. ![Microsoft Exchange Zero-Day Attack Chain - Adversary scans for vulnerable Exchange Servers; Adversary sends HTTP requests and authenticates an exchange server using CVE-2021-26855; Uploads webshell and executes malicious commands using three other Microsoft Exchange Server vulnerabilities discussed here. Post-exploitation activity: Uses ProcDump to dump LSASS process memory to obtain credentials; Executes reconnaissance-related commands; Downloads confidential information and additional tools; Compresses stolen data into ZIP for exfiltration.](https://unit42.paloaltonetworks.com/wp-content/uploads/2021/03/word-image-14.png) Figure 1. Threat actors can chain together four zero-day vulnerabilities to gain unauthorized access to Microsoft Exchange Servers. Microsoft has shared ways to determine whether your system has been compromised by this activity. There is also an emergency out-of-band [security update](https://techcommunity.microsoft.com/t5/exchange-team-blog/released-march-2021-exchange-server-security-updates/ba-p/2175901)to patch these vulnerabilities. ## Courses of Action This section documents the relevant tactics, techniques and procedures (TTPs) observed being used by adversaries leveraging [CVE-2021-26855](https://msrc.microsoft.com/update-guide/vulnerability/CVE-2021-26855), [CVE-2021-26857](https://msrc.microsoft.com/update-guide/vulnerability/CVE-2021-26857), [CVE-2021-26858](https://msrc.microsoft.com/update-guide/vulnerability/CVE-2021-26858) and [CVE-2021-27065](https://msrc.microsoft.com/update-guide/vulnerability/CVE-2021-27065), and maps them directly to Palo Alto Networks product(s) and service(s) which can protect against them. It also further instructs customers on how to ensure their devices are configured correctly. |-----------------------|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------| | **Product / Service** | **Course of Action** | | **Initial Access, Persistence, Command and Control, Exfiltration** || | **Exploit Public-Facing Application \[T1190\], Web Shell \[T1505.003\], Web Protocols \[T1071.001\], Ingress Tool Transfer \[T1105\], Exfiltration Over C2 Channel \[T1041\], Domain Account \[T1136.002\]** || | NGFW | Ensure application security policies exist when allowing traffic from an untrusted zone to a more trusted zone | | NGFW | Ensure 'Service setting of ANY' in a security policy allowing traffic does not exist | | NGFW | Ensure 'Security Policy' denying any/all traffic to/from IP addresses on Trusted Threat Intelligence Sources Exists | | NGFW | Ensure 'SSL Forward Proxy Policy' for traffic destined to the internet is configured | | NGFW | Ensure 'SSL Inbound Inspection' is required for all untrusted traffic destined for servers using SSL or TLS | | NGFW | Ensure that the Certificate used for Decryption is Trusted | | NGFW | Set up File Blocking | | NGFW | Ensure that User-ID is only enabled for internal trusted interfaces | | NGFW | Ensure that 'Include/Exclude Networks' is used if User-ID is enabled | | NGFW | Ensure that the User-ID Agent has minimal permissions if User-ID is enabled | | NGFW | Ensure that the User-ID service account does not have interactive logon rights | | NGFW | Ensure remote access capabilities for the User-ID service account are forbidden. | | NGFW | Define at least one 'Include Network'. | | Threat Prevention\*†\* | Ensure a Vulnerability Protection Profile is set to block attacks against critical and high vulnerabilities, and set to default on medium, low and informational vulnerabilities | | Threat Prevention\*†\* | Ensure a secure Vulnerability Protection Profile is applied to all security rules allowing traffic | | Threat Prevention\*†\* | Ensure an anti-spyware profile is configured to block on all spyware severity levels, categories and threats | | Threat Prevention\*†\* | Ensure DNS sinkholing is configured on all anti-spyware profiles in use | | Threat Prevention\*†\* | Ensure passive DNS monitoring is set to enabled on all anti-spyware profiles in use | | Threat Prevention\*†\* | Ensure a secure anti-spyware profile is applied to all security policies permitting traffic to the internet | | Threat Prevention\*†\* | Ensure that antivirus profiles are set to block on all decoders except 'imap' and 'pop3' | | Threat Prevention\*†\* | Ensure a secure antivirus profile is applied to all relevant security policies | | DNS Security\*†\* | Enable DNS Security in anti-spyware profile | | URL Filtering\*†\* | Ensure that PAN-DB URL Filtering is used | | URL Filtering\*†\* | Ensure that URL Filtering uses the action of 'block' or 'override' on the \ URL categories | | URL Filtering\*†\* | Ensure that access to every URL is logged | | URL Filtering\*†\* | Ensure all HTTP Header Logging options are enabled | | URL Filtering\*†\* | Ensure secure URL filtering is enabled for all security policies allowing traffic to the internet | | WildFire\*†\* | Ensure that WildFire file size upload limits are maximized | | WildFire\*†\* | Ensure forwarding is enabled for all applications and file types in WildFire file blocking profiles | | WildFire\*†\* | Ensure a WildFire Analysis profile is enabled for all security policies | | WildFire\*†\* | Ensure forwarding of decrypted content to WildFire is enabled | | WildFire\*†\* | Ensure all WildFire session information settings are enabled | | WildFire\*†\* | Ensure alerts are enabled for malicious files detected by WildFire | | WildFire\*†\* | Ensure 'WildFire Update Schedule' is set to download and install updates every minute | | Cortex XSOAR | Deploy XSOAR Playbook "HAFNIUM - Exchange 0-day exploits" (*Rapid Breach Response pack* ) | | Cortex XSOAR | Deploy XSOAR Playbook Cortex XDR - Isolate Endpoint | | Cortex XSOAR | Deploy XSOAR Playbook - Block IP | | Cortex XSOAR | Deploy XSOAR Playbook - Block URL | | Cortex XSOAR | Deploy XSOAR Playbook - Hunting and Threat Detection Playbook | | Cortex XSOAR | Deploy XSOAR Playbook - PAN-OS Query Logs for Indicators | | Cortex XSOAR | Deploy XSOAR Playbook - Access Investigation Playbook | | Cortex XSOAR | Deploy XSOAR Playbook - Block Account Generic | | ****Execution, Credential Access, Collection,**** **Lateral Movement** || | **Windows Command Shell \[T1059.003\], LSASS Memory \[T1003.001\], Archive via Utility \[T1560.001\], Web Protocols \[T1070.001\], Exploit Public-Facing Application \[T1190\], Remote System Discovery \[T1018\], System Information Discovery\[T1082\], System Network Configuration Discovery \[T1016\], System Service Discovery \[T1007\], Permission Groups Discovery \[T1069\],**OS Credential Dumping \[T1003\], Remote Services \[T1021\], Account Discovery \[T1087\], Windows Remote Management \[T1021.006\], Windows Remote Management \[T1047\], Scripting \[T1064\], Powershell \[T1059.001\]**** || | Cortex XDR | Enable Anti-Exploit Protection | | Cortex XDR | Enable Anti-Malware Protection | | Cortex XDR | Suspicious Process Creation | | Cortex XDR | Look for the following BIOCs alerts to detect activity\*: *Cortex XDR Analytics BIOC -Uncommon net group execution* *Cortex XDR Analytics - Multiple Discovery Commands* *Cortex XDR BIOC -Exchange process writing aspx files* *Cortex XDR Agent - Behavioral Threat Detected* *Cortex XDR Analytics BIOC - Uncommon remote service start via sc.exe* *Cortex XDR Analytics BIOC - Rare SSH Session* *Cortex XDR Analytics BIOC - Uncommon ARP cache listing via arp.exe* *Cortex XDR Analytics BIOC - Uncommon user management via net.exe* *Cortex XDR Analytics BIOC - WmiPrvSe.exe Rare Child Command Line* *Cortex XDR Analytics BIOC - Script Connecting to Rare External Host* *Cortex XDR BIOC - Remote process execution using WMI* *Cortex XDR BIOC - 64-bit PowerShell spawning a 32-bit PowerShell* *Cortex XDR BIOC - Suspicious PowerShell Command Line* *Cortex XDR BIOC - Dumping Registry hives with passwords* | ^*Table 1. Courses of Action for observed techniques used by multiple threat actors leveraging zero-day Microsoft Exchange Server vulnerabilities.*^^*†These capabilities are part of the NGFW security subscriptions service.*^^*\* These analytic detectors will trigger automatically for Cortex XDR Pro customers.*^ ## Conclusion Due to the alarming activity of threat actors exploiting these zero-day vulnerabilities against vulnerable Microsoft Exchange Servers, we strongly advise immediately updating all Microsoft Exchange Servers to the latest available patched versions released by Microsoft. As of the time of writing, based on signatures and indicators that have been observed, Palo Alto Networks customers are protected across our product ecosystem, with specific protections deployed in the following products and subscriptions: * [Next-Generation Firewall](https://www.paloaltonetworks.com/network-security/next-generation-firewall): * [Threat Prevention](https://www.paloaltonetworks.com/products/secure-the-network/subscriptions/threat-prevention). (Deploy Content Pack 8380 which detects the four 0-day vulnerabilities) * [URL Filtering](https://www.paloaltonetworks.com/products/threat-detection-and-prevention/web-security). * [Cortex XDR](https://www.paloaltonetworks.com/cortex/cortex-xdr). * [Cortex XSOAR](https://www.paloaltonetworks.com/cortex/xsoar). It is imperative for customers to employ [best practices](https://docs.paloaltonetworks.com/best-practices) in order to ensure Palo Alto Networks products are configured in a manner best suited for your protection. ## Additional Resources * [Hunting for the Recent Attacks Targeting Microsoft Exchange](https://blog.paloaltonetworks.com/security-operations/attacks-targeting-microsoft-exchange/) * [HAFNIUM targeting Exchange Servers with 0-day exploits](https://www.microsoft.com/security/blog/2021/03/02/hafnium-targeting-exchange-servers/) * [Operation Exchange Marauder: Active Exploitation of Multiple Zero-Day Microsoft Exchange Vulnerabilities](https://www.volexity.com/blog/2021/03/02/active-exploitation-of-microsoft-exchange-zero-day-vulnerabilities/) * [Mass Exploitation of Exchange Server Zero-Day CVEs: What You Need to Know](https://blog.rapid7.com/2021/03/03/mass-exploitation-of-exchange-server-zero-day-cves-what-you-need-to-know/) Back to top ### Tags * [CVE-2021-26855](https://unit42.paloaltonetworks.com/tag/cve-2021-26855/ "CVE-2021-26855") * [CVE-2021-26857](https://unit42.paloaltonetworks.com/tag/cve-2021-26857/ "CVE-2021-26857") * [CVE-2021-26858](https://unit42.paloaltonetworks.com/tag/cve-2021-26858/ "CVE-2021-26858") * [CVE-2021-27065](https://unit42.paloaltonetworks.com/tag/cve-2021-27065/ "CVE-2021-27065") * [Exploits](https://unit42.paloaltonetworks.com/tag/exploits/ "exploits") * [Microsoft Exchange Server](https://unit42.paloaltonetworks.com/tag/microsoft-exchange-server/ "Microsoft Exchange Server") * [Zero-day](https://unit42.paloaltonetworks.com/tag/zero-day/ "zero-day") [Threat Research Center](https://unit42.paloaltonetworks.com "Threat Research") [Next: Threat Brief: Kerberos KDC Security Feature Bypass Vulnerability (CVE-2020-17049 AKA Bronze Bit)](https://unit42.paloaltonetworks.com/cve-2020-17049/ "Threat Brief: Kerberos KDC Security Feature Bypass Vulnerability (CVE-2020-17049 AKA Bronze Bit)") ### Table of Contents * ### Related Articles * [The Frontier AI Vulnerability Burst: Industrializing Autonomous Zero-Day Discovery in Open-Source Software](https://unit42.paloaltonetworks.com/frontier-ai-vulnerability-burst/ "article - table of contents") * [Threat Brief: Exploitation of PAN-OS Captive Portal Zero-Day for Unauthenticated Remote Code Execution](https://unit42.paloaltonetworks.com/captive-portal-zero-day/ "article - table of contents") * [Fracturing Software Security With Frontier AI Models](https://unit42.paloaltonetworks.com/ai-software-security-risks/ "article - table of contents") ## Related Vulnerabilities Resources ![Pictorial representation of a group of people interacting with a dynamic 3D holographic display of colorful, undulating data waves on a table.](https://unit42.paloaltonetworks.com/wp-content/uploads/2025/09/11_Myth-Busting_Overview_1920x900-786x368.jpg) [![category icon](https://unit42.paloaltonetworks.com/wp-content/uploads/2025/08/Insights-icon-white.svg)Insights](https://unit42.paloaltonetworks.com/category/insights/) August 4, 2026 [#### The Frontier AI Vulnerability Burst: Industrializing Autonomous Zero-Day Discovery in Open-Source Software](https://unit42.paloaltonetworks.com/frontier-ai-vulnerability-burst/) * [AI](https://unit42.paloaltonetworks.com/tag/ai/ "AI") * [Frontier AI](https://unit42.paloaltonetworks.com/tag/frontier-ai/ "Frontier AI") * [Vulnerability Exploitation](https://unit42.paloaltonetworks.com/tag/vulnerability-exploitation/ "Vulnerability Exploitation") [Read now ![Right arrow](https://unit42.paloaltonetworks.com/wp-content/themes/unit42-v6/dist/images/icons/icon-right-arrow-withtail.svg)](https://unit42.paloaltonetworks.com/frontier-ai-vulnerability-burst/ "The Frontier AI Vulnerability Burst: Industrializing Autonomous Zero-Day Discovery in Open-Source Software") ![Pictorial representation of AI-enabled autonomous cyberattacks. A digital illustration depicting abstract, interconnected data streams in vibrant colors on a dark blue background](https://unit42.paloaltonetworks.com/wp-content/uploads/2026/07/AdobeStock_992950050-3-782x440.jpeg) [![category icon](https://unit42.paloaltonetworks.com/wp-content/uploads/2024/06/icon-threat-research.svg)Threat Research](https://unit42.paloaltonetworks.com/category/threat-research/) July 30, 2026 [#### Chinese-Speaking Threat Actor Harnesses AI Models for Autonomous Cyberattacks](https://unit42.paloaltonetworks.com/autonomous-ai-cyber-attack-campaign/) * [ChatGPT](https://unit42.paloaltonetworks.com/tag/chatgpt/ "ChatGPT") * [Claude code](https://unit42.paloaltonetworks.com/tag/claude-code/ "Claude code") * [CVEs](https://unit42.paloaltonetworks.com/tag/cves/ "CVEs") [Read now ![Right arrow](https://unit42.paloaltonetworks.com/wp-content/themes/unit42-v6/dist/images/icons/icon-right-arrow-withtail.svg)](https://unit42.paloaltonetworks.com/autonomous-ai-cyber-attack-campaign/ "Chinese-Speaking Threat Actor Harnesses AI Models for Autonomous Cyberattacks") ![Pictorial representation of three zero-day vulnerabilities in Siemens ROX II OT switches. Digital illustration of a global network featuring interconnected lines and nodes over a map of the world, highlighted with neon lights and digital elements.](https://unit42.paloaltonetworks.com/wp-content/uploads/2026/07/03_Vulnerabilities_1920x900-786x368.jpg) [![category icon](https://unit42.paloaltonetworks.com/wp-content/uploads/2024/06/icon-threat-research.svg)Threat Research](https://unit42.paloaltonetworks.com/category/threat-research/) July 17, 2026 [#### Three Steps to the Terminal: A Siemens ROX II Zero-Day Trilogy](https://unit42.paloaltonetworks.com/siemens-rox-ii-zero-day-vulnerabilities/) * [Command injection](https://unit42.paloaltonetworks.com/tag/command-injection/ "Command injection") * [CVE-2025-40947](https://unit42.paloaltonetworks.com/tag/cve-2025-40947/ "CVE-2025-40947") * [CVE-2025-40948](https://unit42.paloaltonetworks.com/tag/cve-2025-40948/ "CVE-2025-40948") [Read now ![Right arrow](https://unit42.paloaltonetworks.com/wp-content/themes/unit42-v6/dist/images/icons/icon-right-arrow-withtail.svg)](https://unit42.paloaltonetworks.com/siemens-rox-ii-zero-day-vulnerabilities/ "Three Steps to the Terminal: A Siemens ROX II Zero-Day Trilogy") ![Pictorial representation of PAN-OS CVE-2026-0257. A vibrant city skyline at night, with tall skyscrapers and glowing digital beams extending into the sky, suggesting advanced technology and connectivity.](https://unit42.paloaltonetworks.com/wp-content/uploads/2026/06/07_Vulnerabilities_1920x900-786x368.jpg) [![category icon](https://unit42.paloaltonetworks.com/wp-content/uploads/2024/07/top-threats.svg)High Profile Threats](https://unit42.paloaltonetworks.com/category/top-cyberthreats/) June 9, 2026 [#### Threat Brief: Active Exploitation of PAN-OS CVE-2026-0257](https://unit42.paloaltonetworks.com/active-exploitation-of-pan-os-cve-2026-0257/) * [CVE-2026-0257](https://unit42.paloaltonetworks.com/tag/cve-2026-0257/ "CVE-2026-0257") * [Vulnerability](https://unit42.paloaltonetworks.com/tag/vulnerability/ "vulnerability") [Read now ![Right arrow](https://unit42.paloaltonetworks.com/wp-content/themes/unit42-v6/dist/images/icons/icon-right-arrow-withtail.svg)](https://unit42.paloaltonetworks.com/active-exploitation-of-pan-os-cve-2026-0257/ "Threat Brief: Active Exploitation of PAN-OS CVE-2026-0257") ![Pictorial representation of CVE-2026-30300. Digital illustration of a map of North America with interconnected glowing lines and dots symbolizing network connections across the continent.](https://unit42.paloaltonetworks.com/wp-content/uploads/2026/05/06_Vulnerabilities_1920x900-3-1-786x368.jpg) [![category icon](https://unit42.paloaltonetworks.com/wp-content/uploads/2024/07/top-threats.svg)High Profile Threats](https://unit42.paloaltonetworks.com/category/top-cyberthreats/) May 6, 2026 [#### Threat Brief: Exploitation of PAN-OS Captive Portal Zero-Day for Unauthenticated Remote Code Execution](https://unit42.paloaltonetworks.com/captive-portal-zero-day/) * [CVE-2026-0300](https://unit42.paloaltonetworks.com/tag/cve-2026-0300/ "CVE-2026-0300") * [EarthWorm](https://unit42.paloaltonetworks.com/tag/earthworm/ "EarthWorm") * [PAN-OS](https://unit42.paloaltonetworks.com/tag/pan-os/ "PAN-OS") [Read now ![Right arrow](https://unit42.paloaltonetworks.com/wp-content/themes/unit42-v6/dist/images/icons/icon-right-arrow-withtail.svg)](https://unit42.paloaltonetworks.com/captive-portal-zero-day/ "Threat Brief: Exploitation of PAN-OS Captive Portal Zero-Day for Unauthenticated Remote Code Execution") ![Pictorial representation of a severe Linux vulnerability. Close-up of a woman wearing glasses and focusing intently on a computer screen.](https://unit42.paloaltonetworks.com/wp-content/uploads/2026/05/05_Vulnerabilities_1920x900-2-1-786x368.jpg) [![category icon](https://unit42.paloaltonetworks.com/wp-content/uploads/2024/07/top-threats.svg)High Profile Threats](https://unit42.paloaltonetworks.com/category/top-cyberthreats/) May 5, 2026 [#### Copy Fail: What You Need to Know About the Most Severe Linux Threat in Years](https://unit42.paloaltonetworks.com/cve-2026-31431-copy-fail/) * [Containers](https://unit42.paloaltonetworks.com/tag/containers/ "Containers") * [CVE-2026-31431](https://unit42.paloaltonetworks.com/tag/cve-2026-31431/ "CVE-2026-31431") * [Kubernetes](https://unit42.paloaltonetworks.com/tag/kubernetes/ "Kubernetes") [Read now ![Right arrow](https://unit42.paloaltonetworks.com/wp-content/themes/unit42-v6/dist/images/icons/icon-right-arrow-withtail.svg)](https://unit42.paloaltonetworks.com/cve-2026-31431-copy-fail/ "Copy Fail: What You Need to Know About the Most Severe Linux Threat in Years") ![Pictorial representation of CVE-2023-33538. Abstract image of a glowing red Wi-Fi symbol on a circuit board, with intricate patterns and a futuristic appearance.](https://unit42.paloaltonetworks.com/wp-content/uploads/2026/04/04_Vulnerabilities_1920x900-786x368.jpg) [![category icon](https://unit42.paloaltonetworks.com/wp-content/uploads/2024/06/icon-threat-research.svg)Threat Research](https://unit42.paloaltonetworks.com/category/threat-research/) April 16, 2026 [#### A Deep Dive Into Attempted Exploitation of CVE-2023-33538](https://unit42.paloaltonetworks.com/exploitation-of-cve-2023-33538/) * [Botnet](https://unit42.paloaltonetworks.com/tag/botnet/ "botnet") * [Command injection](https://unit42.paloaltonetworks.com/tag/command-injection/ "Command injection") * [CVE-2023-33538](https://unit42.paloaltonetworks.com/tag/cve-2023-33538/ "CVE-2023-33538") [Read now ![Right arrow](https://unit42.paloaltonetworks.com/wp-content/themes/unit42-v6/dist/images/icons/icon-right-arrow-withtail.svg)](https://unit42.paloaltonetworks.com/exploitation-of-cve-2023-33538/ "A Deep Dive Into Attempted Exploitation of CVE-2023-33538") ![Pictorial representation of BeyondTrust vulnerability CVE-2026-1731. Digital art depicting a stylized mountain range with vibrant blue and red hues. The peaks are accentuated by glowing particles and an abstract, starry backdrop, creating a futuristic landscape.](https://unit42.paloaltonetworks.com/wp-content/uploads/2026/02/14_Overview_1920x900-786x368.jpg) [![category icon](https://unit42.paloaltonetworks.com/wp-content/uploads/2024/07/top-threats.svg)High Profile Threats](https://unit42.paloaltonetworks.com/category/top-cyberthreats/) February 19, 2026 [#### VShell and SparkRAT Observed in Exploitation of BeyondTrust Critical Vulnerability (CVE-2026-1731)](https://unit42.paloaltonetworks.com/beyondtrust-cve-2026-1731/) * [Bash](https://unit42.paloaltonetworks.com/tag/bash/ "bash") * [CVE-2026-1731](https://unit42.paloaltonetworks.com/tag/cve-2026-1731/ "CVE-2026-1731") * [PowerShell](https://unit42.paloaltonetworks.com/tag/powershell/ "PowerShell") [Read now ![Right arrow](https://unit42.paloaltonetworks.com/wp-content/themes/unit42-v6/dist/images/icons/icon-right-arrow-withtail.svg)](https://unit42.paloaltonetworks.com/beyondtrust-cve-2026-1731/ "VShell and SparkRAT Observed in Exploitation of BeyondTrust Critical Vulnerability (CVE-2026-1731)") ![](https://unit42.paloaltonetworks.com/wp-content/uploads/2026/02/AdobeStock_1020436911-786x440.jpeg) [![category icon](https://unit42.paloaltonetworks.com/wp-content/uploads/2024/07/top-threats.svg)High Profile Threats](https://unit42.paloaltonetworks.com/category/top-cyberthreats/) February 17, 2026 [#### Critical Vulnerabilities in Ivanti EPMM Exploited](https://unit42.paloaltonetworks.com/ivanti-cve-2026-1281-cve-2026-1340/) * [CVE-2026-1281](https://unit42.paloaltonetworks.com/tag/cve-2026-1281/ "CVE-2026-1281") * [CVE-2026-1340](https://unit42.paloaltonetworks.com/tag/cve-2026-1340/ "CVE-2026-1340") * [Ivanti](https://unit42.paloaltonetworks.com/tag/ivanti/ "Ivanti") [Read now ![Right arrow](https://unit42.paloaltonetworks.com/wp-content/themes/unit42-v6/dist/images/icons/icon-right-arrow-withtail.svg)](https://unit42.paloaltonetworks.com/ivanti-cve-2026-1281-cve-2026-1340/ "Critical Vulnerabilities in Ivanti EPMM Exploited") ![Pictorial representation of CVE-2025-0921. Digital illustration of a map of North America with interconnected glowing lines and dots symbolizing network connections across the continent.](https://unit42.paloaltonetworks.com/wp-content/uploads/2026/01/06_Vulnerabilities_1920x900-2-1-786x368.jpg) [![category icon](https://unit42.paloaltonetworks.com/wp-content/uploads/2024/06/icon-threat-research.svg)Threat Research](https://unit42.paloaltonetworks.com/category/threat-research/) January 30, 2026 [#### Privileged File System Vulnerability Present in a SCADA System](https://unit42.paloaltonetworks.com/iconics-suite-cve-2025-0921/) * [CVE-2025-0921](https://unit42.paloaltonetworks.com/tag/cve-2025-0921/ "CVE-2025-0921") * [Privilege escalation](https://unit42.paloaltonetworks.com/tag/privilege-escalation/ "privilege escalation") * [SCADA](https://unit42.paloaltonetworks.com/tag/scada/ "SCADA") [Read now ![Right arrow](https://unit42.paloaltonetworks.com/wp-content/themes/unit42-v6/dist/images/icons/icon-right-arrow-withtail.svg)](https://unit42.paloaltonetworks.com/iconics-suite-cve-2025-0921/ "Privileged File System Vulnerability Present in a SCADA System") * ![Slider arrow](https://unit42.paloaltonetworks.com/wp-content/themes/unit42-v6/dist/images/icons/slider-arrow-left.svg) * ![Slider arrow](https://unit42.paloaltonetworks.com/wp-content/themes/unit42-v6/dist/images/icons/slider-arrow-left.svg) ![Close button](https://unit42.paloaltonetworks.com/wp-content/themes/unit42-v6/dist/images/icons/close-modal.svg) ![Enlarged Image]() ![Newsletter](https://unit42.paloaltonetworks.com/wp-content/uploads/2026/03/unit42-footer-subscribe-desktop.png) ![UNIT 42 Small Logo](https://unit42.paloaltonetworks.com/wp-content/themes/unit42-v6/dist/images/palo-alto-logo-small.svg) Get updates from Unit 42 ## Peace of mind comes from staying ahead of threats. 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