CVE-2021-39144: VMware Patches Critical Cloud Foundation Vulnerability in XStream Open Source Library

VMware issues patches for end-of-life versions of Cloud Foundation Network Security Virtualization for vSphere (NSX-V) to address a critical vulnerability in an open source library.


On October 25, VMware published VMSA-2022-0027, an advisory for multiple vulnerabilities in its VMware Cloud Foundation solution.

VMware Cloud Foundation XStream Library Deserialization of Untrusted Data Vulnerability
VMware Cloud Foundation XML External Entity (XXE) Vulnerability


CVE-2021-39144 is a remote code execution vulnerability in XStream, an open source library used for object serialization. This vulnerability was originally patched on August 22, 2021 in XStream version 1.4.18. VMware Cloud Foundation uses XStream for input serialization in its Network Security Virtualization for vSphere (NSX-V) solution. An attacker could exploit this vulnerability by targeting an unauthenticated endpoint in NSX-V to gain remote code execution privileges as root.

CVE-2022-31678 is an XXE vulnerability in VMware Cloud Foundation NSX-V. A remote, unauthenticated attacker could exploit this vulnerability to cause a denial-of-service condition or cause an unintended information disclosure. It is a moderately rated vulnerability, receiving a CVSSv3 score of 5.3.

VMware issues fix for end-of-life versions of NSX-V

In August 2021, VMware announced that general support for NSX-V would end on January 16, 2022 and that technical guidance would end on January 16, 2023. However, in its advisory, VMware notes that “due to the critical severity of NSX-V” a patch was made available to address both flaws.

While no specific details about CVE-2021-39144 were made public by VMware, the fact that they highlighted the attack vector as a “unauthenticated endpoint […] in VMware Cloud Foundation (NSX-V)” coupled with the decision to release a patch for an end-of-life product, suggests that exploitation of this flaw is straightforward.

Supply chain attacks remain a major area of concern

The presence of this vulnerability in the XStream library and its use in VMware Cloud Foundation NSX-V evokes memories of Log4Shell. While CVE-2021-39144 is not the same caliber as Log4Shell, it serves as a reminder of the challenges supply chain vulnerabilities pose to an organization’s security posture.

Proof of concept

The discovery of both flaws are attributed to researchers Steven Seeley of Source Incite and Sina Kheirkhah of MDSec. A blog post was published on Source Incite that details their findings. The blog post includes a proof-of-concept exploit script that can be used to get a reverse shell on a vulnerable VMware Cloud Foundation NSX-V instance.


VMware Cloud Foundation 4.x is not affected by either CVE-2021-39144 or CVE-2022-31678. However, VMware’s advisory notes that VMware Cloud Foundation (NSX-V) versions 3.x are affected:

Affected Versions
Patching Instructions
VMware Cloud Foundation prior to 3.9.1
Update to VMware Cloud Foundation and above and apply workaround instructions
VMware Cloud Foundation 3.9.1 and above
Follow workaround instructions

For customers using VMware Cloud Foundation versions prior to 3.9.1, VMware recommends updating to VMware Cloud Foundation first. Once updated, customers are instructed to follow VMware’s workaround instructions in the Knowledge Base article, Applying NSX-V 6.4.14 patch on VMware Cloud Foundation 3.x (89809).

Identifying affected systems

A list of Tenable plugins to identify these vulnerabilities will appear here as they’re released. This link uses a search filter to ensure that all matching plugin coverage will appear as it is released. Additionally, plugin coverage specific to the XStream library (CVE-2021-39144) can be found here.

Get more information

VMSA-2022-0027: VMware Advisory for CVE-2021-39144, CVE-2022-31678
Source Incite Blog Post on CVE-2021-39144 by Sina Kheirkhah
XStream Advisory for CVE-2021-39144

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