F5 BIG-IP Stack-Based Buffer Overflow Vulnerability
F5 — BIG-IP
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.
9.8
2.2%
Vector breakdown
- Attack vector
- Network
- Attack complexity
- Low
- Privileges required
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- High
- Availability
- High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
- Published
- Oct 15, 2025
- Modified
- Mar 31, 2026
- Added to KEV
- Mar 27, 2026
- Federal patch due
- Mar 30, 2026
CISA 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.
Weakness classification
Proof-of-concept & exploitation references
Weaponization
Public repositories whose name or description references CVE-2025-53521, found via a live GitHub search at request time. These are community-sourced signals, not a verified working exploit — cross-check each one before relying on it, and treat higher star counts and recent activity as (weak) corroboration, not proof.
No public GitHub repositories referencing CVE-2025-53521 were found at last check. Absence here is not proof no exploit exists — see the references below for vendor advisories and write-ups.
References
Frequently asked questions
What is CVE-2025-53521?
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.
How severe is CVE-2025-53521?
CVE-2025-53521 has a CVSS base score of 9.8 out of 10 (CVSS 3.1).
Is CVE-2025-53521 actively exploited in the wild?
Yes. CVE-2025-53521 is listed in the CISA Known Exploited Vulnerabilities (KEV) catalog, added Mar 27, 2026, meaning CISA has confirmed evidence of active exploitation.
What is the EPSS score for CVE-2025-53521?
2.2% - meaning FIRST.org's EPSS model estimates a 2.2% probability this vulnerability will be exploited in the wild within 30 days (81% percentile among all scored CVEs).
What type of vulnerability is CVE-2025-53521?
CVE-2025-53521 is classified under CWE-121 (CWE-121 Stack-based Buffer Overflow).
Cross-checked against
Impactr finds and proves whether CVE-2025-53521 — or flaws like it — are actually reachable in your own web apps and APIs, with a reproducible exploit as evidence.