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CVE-2014-3556

The STARTTLS implementation in mail/ngx_mail_smtp_handler.c in the SMTP proxy in nginx 1.5.x and...

6.8 MediumFix available

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.

Exploit likelihood

7.83%Up 5.5 points since Feb 4, 2022
90%50%10%1%

What each source reports

NVD Score used 6.8

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.

Record
CVE-2014-3556
CVSS 2.0
6.8 MediumAV:N/AC:M/Au:N/C:P/I:P/A:P
Weakness
CWE-77
Updated
2026-11-02
CVE List No score

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.

Record
CVE-2014-3556
Updated
2026-11-02
EUVDEUVD-2014-3539 No score

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.

Record
EUVD-2014-3539
Updated
2026-11-03
GitHub AdvisoriesGHSA-8277-2g6w-24gq No score

The STARTTLS implementation in mail/ngx_mail_smtp_handler.c in the SMTP proxy in nginx 1.5.x and...

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.

Record
GHSA-8277-2g6w-24gq
Weakness
CWE-77
Updated
2026-11-02
OSV No score

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.

Record
CVE-2014-3556
Updated
2026-11-02
OSVDEBIAN-CVE-2014-3556 No score

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.

Record
DEBIAN-CVE-2014-3556
Updated
2026-11-02
OSVopenSUSE-SU-2024:10044-1 No score

nginx-1.11.4-2.5 on GA media

These are all security issues fixed in the nginx-1.11.4-2.5 package on the GA media of openSUSE Tumbleweed.

Record
openSUSE-SU-2024:10044-1
Updated
2026-11-02
OSVUBUNTU-CVE-2014-3556 No score

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.

Record
UBUNTU-CVE-2014-3556
Updated
2026-11-02

Affected products

Affected packages

Affected packages
PackageAffectedFixed
nginx
Debian:12
before 1.6.1-1
1.6.1-1
nginx
Debian:13
before 1.6.1-1
1.6.1-1
nginx
Debian:14
before 1.6.1-1
1.6.1-1
nginx
openSUSE:Tumbleweed
From an advisory covering 11 CVEs
before 1.11.4-2.5
1.11.4-2.5

History

History
RecordedChangedSources
affected, facts
affected
aliasesEUVD
first indexedCVE List, GitHub Advisories, NVD, OSV

Dates are when Every CVE recorded each change. Upstream dates may differ.

In short

CVE-2014-3556 is a medium vulnerability (CVSS 6.8) in F5 Nginx, published December 29, 2014. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 7.83%, the 94th percentile. Fixed in nginx 1.6.1-1.

References

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