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Fencer Intel
medium 6.8

CVE-2014-3556 json

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…

published 2014-12-29 11 y ago modified 2026-06-17 4 mo ago also EUVD-2014-3539

cvss
6.8
version 2.0, NVD
cisa kev
Not listed
not in CISA's catalog
epss
7.8%
EPSS 7.8% chance of exploitation in 30 days, percentile 94%
public exploits
0
none known

Summary

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.

Patch / fix

  • f5 nginx 1.6.1, 1.7.4
  • nginx Debian 14, Debian 13, Debian 12 1.6.1-1

debian advisories DEBIAN-CVE-2014-3556

  • nginx openSUSE Tumbleweed 1.11.4-2.5

opensuse advisories openSUSE-SU-2024:10044-1

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2014-3556 updated cvss 2.9

nginx: SMTP STARTTLS plaintext injection flaw

  • Red Hat Software Collections nginx16-nginx
    affected: no fix available
  • Red Hat Software Collections nginx14-nginx
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

Exploit prediction

7.83% chance of exploitation in the next 30 days, higher than 94% of all scored CVEs (FIRST EPSS, 2026-11-09).

CVSS scores

assigned by version score vector
NVD 2.0 6.8 AV:N/AC:M/Au:N/C:P/I:P/A:P

Classification

Weakness
  • CWE-77 Improper Neutralization of Special Elements used in a Command
Technology feeds

References

Sources

Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.