SB2025081427 - Information disclosure in NGINX ngx_mail_smtp_module 

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Main Vulnerability Database SB2025081427

SB2025081427 - Information disclosure in NGINX ngx_mail_smtp_module

Published: August 14, 2025

Security Bulletin ID SB2025081427
Severity
Low
Patch available
YES
Number of vulnerabilities 1
Exploitation vector Remote access
Highest impact Information disclosure

Breakdown by Severity

Low 100%
  • Low
  • Medium
  • High
  • Critical

Description

This security bulletin contains information about 1 security vulnerability.


1) Out-of-bounds read (CVE-ID: CVE-2025-53859)

The vulnerability allows a remote attacker to gain access to sensitive information.

The vulnerability exists due to a boundary condition in the ngx_mail_smtp_module. A remote attacker can force the server to 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.


Remediation

Install update from vendor's website.

References