Use After Free in F5 Big-ip
CVE-2026-41218
When BIG-IP PEM iRules are configured on a virtual server (iRules using commands starting with CLASSIFICATION::, CLASSIFY::, PEM::, PSC::, and the urlcatquery command), undisclosed traffic can cause the Traffic Management Microkernel (TMM)…
Vulnerability class: Use-After-Free
EPSS: 0.003 (17.9th percentile) — read the EPSS interpretation.
CVSS v3 metric
CVSS v3 base score 7.5 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.
Affected products
- F5 Big-ip — versions 21.1.0, 21.0.0, 17.5.0
- F5 Big-ip_access_policy_manager — versions 21.0.0
- F5 Big-ip_advanced_firewall_manager — versions 21.0.0
- F5 Big-ip_advanced_web_application_firewall — versions 21.0.0
- F5 Big-ip_analytics — versions 21.0.0
- F5 Big-ip_application_acceleration_manager — versions 21.0.0
- F5 Big-ip_application_security_manager — versions 21.0.0
- F5 Big-ip_application_visibility_and_reporting — versions 21.0.0
- F5 Big-ip_automation_toolchain — versions 21.0.0
- F5 Big-ip_carrier-grade_nat — versions 21.0.0
Weakness classification (CWE)
References
- f5sirt@f5.com (vendor-advisory, Mitigation, patch, Vendor Advisory)
Frequently asked questions
- What is CVE-2026-41218?
- CVE-2026-41218 is a high-severity vulnerability in F5 Big-ip, classified under Use After Free. CVSS score: 7.5/10. Published 2026-05-13.
- How severe is CVE-2026-41218?
- High severity. CVSS v3 base score is 7.5 out of 10.