CVE-2021-21973 vulnerability in VMware Products
Published on February 24, 2021

The vSphere Client (HTML5) contains an SSRF (Server Side Request Forgery) vulnerability due to improper validation of URLs in a vCenter Server plugin. A malicious actor with network access to port 443 may exploit this issue by sending a POST request to vCenter Server plugin leading to information disclosure. This affects: VMware vCenter Server (7.x before 7.0 U1c, 6.7 before 6.7 U3l and 6.5 before 6.5 U3n) and VMware Cloud Foundation (4.x before 4.2 and 3.x before 3.10.1.2).

Vendor Advisory NVD

Known Exploited Vulnerability

This VMware vCenter Server and Cloud Foundation Server Side Request Forgery (SSRF) Vulnerability is part of CISA's list of Known Exploited Vulnerabilities. VMware vCenter Server and Cloud Foundation Server contain a SSRF vulnerability due to improper validation of URLs in a vCenter Server plugin. This allows for information disclosure.

The following remediation steps are recommended / required by March 21, 2022: Apply updates per vendor instructions.

Vulnerability Analysis

CVE-2021-21973 can be exploited with network access, and does not require authorization privileges or user interaction. This vulnerability is considered to have a low attack complexity. It has the highest possible exploitability rating (3.9). The potential impact of an exploit of this vulnerability is considered to have a small impact on confidentiality, a small impact on integrity and availability.

What is a XSPA Vulnerability?

The web server receives a URL or similar request from an upstream component and retrieves the contents of this URL, but it does not sufficiently ensure that the request is being sent to the expected destination. By providing URLs to unexpected hosts or ports, attackers can make it appear that the server is sending the request, possibly bypassing access controls such as firewalls that prevent the attackers from accessing the URLs directly. The server can be used as a proxy to conduct port scanning of hosts in internal networks, use other URLs such as that can access documents on the system (using file://), or use other protocols such as gopher:// or tftp://, which may provide greater control over the contents of requests.

CVE-2021-21973 has been classified to as a XSPA vulnerability or weakness.

Products Associated with CVE-2021-21973

You can be notified by stack.watch whenever vulnerabilities like CVE-2021-21973 are published in these products:

VMware Cloud Foundation

VMware Vcenter Server

What versions are vulnerable to CVE-2021-21973?