F5 BIG-IP Stack-Based Buffer Overflow Vulnerability (CVE-2025-53521)
Severity: critical · Patch status: unknown · Since 2026-03-27 · CVE-2025-53521
F5 BIG-IP APM contains a stack-based buffer overflow vulnerability that could allow a threat actor to achieve remote code execution. CISA added CVE-2025-53521 to its Known Exploited Vulnerabilities catalog on Mar 27, 2026, which means attackers are exploiting it in the wild.
What to do
- Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.
- US federal agencies must remediate by Mar 30, 2026 (BOD 22-01); treat that as the outer limit.
Sources
All live incidents on Threat Watch
