Out-of-bounds Read in F5 Nginx Open Source
CVE-2025-53859
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 sen…
Vulnerability class: Buffer Overflow
EPSS: 0.004 (28.9th percentile) — read the EPSS interpretation.
CVSS v3 metric
CVSS v3 base score 3.7 (Low). Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N.
Affected products
- F5 Nginx Open Source — versions 0.7
- F5 Nginx_open_source
- F5 Nginx Plus — versions R35, R34, R33
- F5 Nginx_plus — versions r30, r31, r32
Weakness classification (CWE)
Public proof-of-concept exploits
References
- f5sirt@f5.com (vendor-advisory, Vendor Advisory)
- af854a3a-2127-422b-91ae-364da2661108
Frequently asked questions
- What is CVE-2025-53859?
- CVE-2025-53859 is a low-severity vulnerability in F5 Nginx Open Source, classified under Out-of-bounds Read. CVSS score: 3.7/10. Published 2025-08-13.
- How severe is CVE-2025-53859?
- Low severity. CVSS v3 base score is 3.7 out of 10.
- Is CVE-2025-53859 known to be exploited?
- 1 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.