Vulnerability 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.
CVSS Score
LOW
Affected Products
| Vendor | Product | Versions |
|---|---|---|
| F5 | Nginx Plus | r30 |
| F5 | Nginx Open Source | >= 0.7.22, < 1.29.1 |
Related Weaknesses (CWE)
References
- https://my.f5.com/manage/s/article/K000152786Vendor Advisory
- http://www.openwall.com/lists/oss-security/2025/08/13/5
FAQ
What is CVE-2025-53859?
CVE-2025-53859 is a vulnerability with a CVSS score of 3.7 (LOW). 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 s...
How severe is CVE-2025-53859?
CVE-2025-53859 has been rated LOW with a CVSS base score of 3.7/10. Review the CVSS metrics above for detailed severity breakdown.
Is there a patch for CVE-2025-53859?
Check the references section above for vendor advisories and patch information. Affected products include: F5 Nginx Plus, F5 Nginx Open Source.