CVE entry · CVE-2025-53521
CVE-2025-53521: F5 BIG-IP Stack-Based Buffer Overflow Vulnerability
F5 BIG-IP APM contains a stack-based buffer overflow vulnerability that could allow a threat actor to achieve remote code execution.
- Actively exploited: added to CISA’s KEV catalog on March 27, 2026.
- Use by ransomware: not established so far.
- Remediation deadline for US federal agencies: March 30, 2026.
- CERT-FR alert CERTFR-2026-ALE-004 of March 31, 2026.
Description from CISA’s KEV catalog.
CERT-FR alerts and notices
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CERTFR-2026-ALE-004Vulnérabilité dans F5 BIG-IP Access Policy Manager (31 mars 2026)
What to do
- Check whether your estate includes F5 BIG-IP, including internet-facing devices.
- Apply the vendor’s patch or mitigations (references below). Failing that, isolate the product or stop using it, as CISA requires of US federal agencies.
- An exploited vulnerability has often been used before it was fixed: look for signs of compromise, especially on internet-facing devices.