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Vulnerability record · CVE-2014-3556 · published 29 December 2014

CVE-2014-3556: F5 nginx command injection vulnerability

F5 · Nginx

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.

6.8 CVSS 2.0 Medium EPSS 7.8% · top 5.5% CWE-77 · Command injection
6.8CVSS 2.0 base score
7.8%EPSS exploitation probability, 30 days
NoNot in CISA KEV
1Affected product versions listed by NVD
8References
17 Jun 2026Last modified by NVD

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.

AV:N/AC:M/Au:N/C:P/I:P/A:P

Affected products

1 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
http://mailman.nginx.org/pipermail/nginx-announce/2014/000144.html PatchVendor Advisory
http://marc.info/?l=bugtraq&m=142103967620673&w=2 Issue TrackingThird Party Advisory
http://nginx.org/download/patch.2014.starttls.txt PatchVendor Advisory
https://bugzilla.redhat.com/show_bug.cgi?id=1126891 Issue TrackingThird Party Advisory
http://mailman.nginx.org/pipermail/nginx-announce/2014/000144.html PatchVendor Advisory
http://marc.info/?l=bugtraq&m=142103967620673&w=2 Issue TrackingThird Party Advisory
http://nginx.org/download/patch.2014.starttls.txt PatchVendor Advisory
https://bugzilla.redhat.com/show_bug.cgi?id=1126891 Issue TrackingThird Party Advisory

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Same products first, then exploited flaws of the same weakness class.

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Source: NIST National Vulnerability Database (record CVE-2014-3556), CISA KEV, FIRST EPSS (scores of 2026-09-26). This page is refreshed as NVD updates the record.