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.
Fixed in Linux distributions
Distributions backport fixes, so the version that fixes this vulnerability differs per release — upgrade to at least the version shown. From the distributions' security trackers and advisories.
Debian
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian 14 | nginx | 1.6.1-1 | — |
| Debian 13 | nginx | 1.6.1-1 | — |
| Debian 12 | nginx | 1.6.1-1 | — |
openSUSE
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| openSUSE Tumbleweed | nginx | 1.11.4-2.5 | openSUSE-SU-2024:10044-1 |
Advisories 1
- openSUSE-SU-2024:10044-1 nginx-1.11.4-2.5 on GA media SUSE / openSUSE Security Updates · Feb 4, 2026