CVE-2025-53859

Name	CVE-2025-53859
Description	NGINX Open Source and NGINX Plus have a vulnerability in the ngx_mail_smtp_module that might allow an unauthenticated attacker to over-read NGINX SMTP authentication process memory; as a result, the server side may leak arbitrary bytes sent in a request to the authentication server. This issue happens during the NGINX SMTP authentication process and requires the attacker to make preparations against the target system to extract the leaked data. The issue affects NGINX only if (1) it is built with the ngx_mail_smtp_module, (2) the smtp_auth directive is configured with method "none," and (3) the authentication server returns the "Auth-Wait" response header. Note: Software versions which have reached End of Technical Support (EoTS) are not evaluated.
Source	CVE (at NVD; CERT, LWN, oss-sec, fulldisc, Debian ELTS, Red Hat, Ubuntu, Gentoo, SUSE bugzilla/CVE, GitHub advisories/code/issues, web search, more)
Debian Bugs	1111138

Vulnerable and fixed packages

The table below lists information on source packages.

Source Package	Release	Version	Status
nginx (PTS)	bullseye	1.18.0-6.1+deb11u3	vulnerable
	bullseye (security)	1.18.0-6.1+deb11u5	vulnerable
	bookworm	1.22.1-9+deb12u3	fixed
	trixie	1.26.3-3+deb13u1	fixed
	forky, sid	1.28.0-6	fixed

The information below is based on the following data on fixed versions.

Package	Type	Release	Fixed Version	Debian Bugs
nginx	source	experimental	1.28.0-2
nginx	source	bookworm	1.22.1-9+deb12u3
nginx	source	trixie	1.26.3-3+deb13u1
nginx	source	(unstable)	1.28.0-3	1111138

[bullseye] - nginx <postponed> (minor issue)
https://www.openwall.com/lists/oss-security/2025/08/13/5
https://nginx.org/download/patch.2025.smtp.txt