CVE-2025-53521
Actively exploited. CVE-2025-53521 is listed in the CISA Known Exploited Vulnerabilities catalog (added 2026-03-27) — exploitation has been observed in the wild, and US federal agencies are required to remediate it under BOD 22-01. Treat patching as urgent.
On October 15, 2025, F5 published a security notice regarding, among other things, the vulnerability CVE-2025-53521. This affects BIG-IP APM and allows an unauthenticated attacker to execute code remotely. On March 29, 2026, the vendor indicates that this vulnerability is actively being exploited. The...
CSIRTS triage
- What
- F5 BIG-IP APM allows an unauthenticated attacker to execute code remotely.
- Who is affected
- Deployments of F5 BIG-IP APM.
- Urgency
- Remediation is urgent due to active exploitation.
- Action
- Apply the security updates provided by F5.
AI-assisted analysis generated from the source advisory — verify against the original.
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Exploitation outlook
- Exploitation confirmedAlready exploited in the wild (CISA KEV) — the prediction phase is over. Patch now. Riskier than 81% of all EPSS-scored CVEs.
Advisory coverage (2)
- unknownexploitedVulnerability in F5 BIG-IP Access Policy Manager (March 31, 2026)cert-fr-alerte · 2026-03-31
- criticalexploitedCVE-2025-53521: F5 BIG-IP Stack-Based Buffer Overflow Vulnerabilitycisa-kev · 2026-03-27
External references
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