Actively exploited · Published Oct 15, 2025 · Assigned by f5
CVE-2025-53521BigIP APM Vulnerability
Critical 9.8 Exploited
In plain English
A critical-severity stack buffer overflow in BIG-IP from F5. Attackers are actively exploiting it in the wild (listed by CISA on March 27, 2026). The chance it is exploited in the next 30 days is estimated at 2.3% (higher than 83% of all known vulnerabilities). Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.
CISA guidance
Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.
Federal agencies must remediate by Mar 30, 2026.
Official description
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 (as reported)
Weakness: CWE-121 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
References
- https://my.f5.com/manage/s/article/K000156741 vendor-advisory
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2025-53521 government-resource