CVE-2025-53521: F5 BIG-IP Stack-Based Buffer Overflow Vulnerability

Critical severity, CVSS 9.8. Actively exploited: in CISA KEV since 2026-03-27. EPSS: 2.3% chance of exploitation in the next 30 days.

When a BIG-IP APM access policy is configured on a virtual server, specific malicious traffic can lead to Remote Code Execution (RCE).   Note: Software versions which have reached End of Technical Support (EoTS) are not evaluated.

Affected products

• F5 BIG-IP Access Policy Manager: from 15.1.0, before 15.1.10.8 (fixed in 15.1.10.8); from 16.1.0, before 16.1.6.1 (fixed in 16.1.6.1); from 17.1.0, before 17.1.3 (fixed in 17.1.3); from 17.5.0, before 17.5.1.3 (fixed in 17.5.1.3)

Published 2025-10-15. Last modified 2026-10-08.