CVE DATABASE / CVE-2025-53521
CVE-2025-53521
F5 BIG-IP Stack-Based Buffer Overflow Vulnerability
Confirmed exploited in the wild. Added 2026-03-27.
Federal remediation due 2026-03-30.
Required action: Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.
Summary
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.
CVSS 3.1 breakdown
| Base score | 9.8 (CRITICAL) |
| Vector | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H |
| Attack vector | NETWORK |
| Attack complexity | LOW |
| Privileges required | NONE |
| User interaction | NONE |
| Scope | UNCHANGED |
| Confidentiality | HIGH |
| Integrity | HIGH |
| Availability | HIGH |
Weakness type (CWE)
Affected products
Use our free CVE Lookup tool for the latest NVD record, or browse the full CISA KEV catalog.
References
- https://my.f5.com/manage/s/article/K000156741
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2025-53521
Data: NIST NVD + CISA KEV. NVD last modified 2026-04-02. Always verify against the vendor advisory before acting.