CVE-2025-53521: listed in the CISA KEV catalog

CVE-2025-53521 · CVSS 9.8 CRITICAL · EPSS 2% · KEV 2026-03-27

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.

Is CVE-2025-53521 exploited?

• Listed in the CISA KEV catalog on 2026-03-27.
• Federal remediation due 2026-03-30.
• Past that date by 138 days.
• EPSS puts exploitation in the next 30 days at 2%.
• Public exploit code: none found in monitored sources.

Which products and versions are affected?

No affected package list recorded here yet.

Is there a patch?

No patch identifier recorded here yet.

What PlainSec published about CVE-2025-53521

• F5 BIG-IP APM Flaw Reclassified as Critical RCE with Active Exploitation (2026-04-26)
• CISA Adds F5 BIG‑IP APM RCE Flaw to KEV (2026-04-01)

Primary sources

• NVD record
• CISA KEV catalog

What this record does not say

• No affected package data.
• No patch identifier.

KEV and EPSS are re-checked daily. Record last updated 2026-08-11.