CVE-2011-2165: WatchGuard Xcs

Medium severity, CVSS 6.8. EPSS: 5.2% chance of exploitation in the next 30 days.

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.

Affected products

• WatchGuard Xcs: version 9.0 only; version 9.1 only

Published 2011-05-23. Last modified 2026-06-16.