CVE-2025-53859 — NGINX ngx_mail_smtp_module vulnerability

Description (CNA)

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.

Affected (CNA)

Vendor / product	Versions
F5 / NGINX Plus	unaffected R35; affected R34 before R34 P2; affected R33 before R33 P3; affected R32 before R32 P3; affected R31 before ; affected R30 before
F5 / NGINX Open Source	affected 0.7 before 1.29.1

CWE

CWE-125

References

https://my.f5.com/manage/s/article/K000152786

ADP enrichment

CISA-ADP

No English description supplied.

No references supplied.

CVE

No English description supplied.

http://www.openwall.com/lists/oss-security/2025/08/13/5