CVE-2014-3556

medium

Published 2014-12-29 · Modified 2026-05-06

CVSS v3

—

CVSS v2

6.8

VIR risk

6.8

Description

The STARTTLS implementation in mail/ngx_mail_smtp_handler.c in the SMTP proxy in nginx 1.5.x and 1.6.x before 1.6.1 and 1.7.x before 1.7.4 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.

Predictions

Exploit likelihood

20%

Patch ETA

—

Heuristic predictions, AS-IS, for prioritization only.

Mitigations

vendor Authored 2026-05-27

Vendor advisory: debian — https://security-tracker.debian.org/tracker/CVE-2014-3556

vendor Authored 2026-05-27

Vendor advisory: secalert@redhat.com — http://nginx.org/download/patch.2014.starttls.txt

vendor Authored 2026-05-27

Vendor advisory: secalert@redhat.com — http://mailman.nginx.org/pipermail/nginx-announce/2014/000144.html

OS impact

OS	Version	Status	Fixed in
debian	bookworm	fixed	`1.6.1-1`
debian	bullseye	fixed	`1.6.1-1`
debian	forky	fixed	`1.6.1-1`
debian	sid	fixed	`1.6.1-1`
debian	trixie	fixed	`1.6.1-1`

Application impact

Vendor	Product	Versions	Fixed
f5	nginx	`{"startIncluding":"1.5.6","endExcluding":"1.6.1"}`	`1.6.1`
nginx	nginx	`{"startIncluding":"1.5.6","endExcluding":"1.6.1"}`	`1.6.1`
nginx	nginx	`{"startIncluding":"1.7.0","endExcluding":"1.7.4"}`	`1.7.4`

References

CWEs

CWE-77

Verify integrity in audit chain (admin only). AS-IS.