Detect CVE-2021-39144: Critical Remote Code Execution Vulnerability in VMware Cloud Foundation via XStream Open Source Library

Another day, another exploit emerges in the wild to cause a headache for security practitioners. VMware warns of a public exploit code available for a recently-patched critical remote code execution (RCE) vulnerability (CVE-2021-39144) in VMware Cloud Foundation and NSX Manager. Leveraging this flaw, unauthenticated threat actors might execute the malicious code with the highest system privileges, while no user interaction required. 

CVE-2021-39144 Detection

With public exploit code available, a vulnerability of 9.8/10 severity poses a critical threat to organizations worldwide. To protect your organizational infrastructure and detect potentially malicious activity at the earliest attack stages, grab a Sigma rule release by our keen Threat Bounty developer Wirapong Petshagun.

The detections are compatible with 18 SIEM, EDR, and XDR technologies and are aligned with the MITRE ATT&CK® framework addressing the Initial Access tactics, with Exploit Public-Facing Applications (T1190) as the corresponding technique.

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Hit the Explore Detections button to instantly access Sigma rules for CVE-2021-39144, corresponding CTI links, ATT&CK references, and threat hunting ideas. 

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CVE-2021-39144 Analysis

The critical VMware Cloud Foundation vulnerability (CVE-2021-39144) occurs due to a misconfiguration in XStream open source library. According to the VMware advisory, an unauthenticated endpoint that leverages XStream for input serialization in VMware Cloud Foundation (NSX-V) enables pre-authenticated RCE with root privileges. The bug affects Cloud Foundation versions 3.11 and lower, while versions 4.x are considered secure. 

The vulnerability received the highest severity rating of 9.8 out of 10 and was immediately patched by the vendor on October 25, 2022. Notably, even though VMware ended the general support for NSX-V in January 2022, a patch was made available for end-of-life products. Also, dedicated guidelines were released to instruct customers on upgrading NSX-V 6.4.14 appliances on Cloud Foundation 3.x. Users are urged to update ASAP since the availability of public exploit code presumes an avalanche of in-the-wild attacks resembling the Log4Shell outbreak. 

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