CVE-2026-41218: f5 big-ip Use After Free

Vulnerability summary

CVE-2026-41218 is a high (CVSS 8.7) Use After Free vulnerability in f5 big-ip. EPSS estimates a 0.46% chance of exploitation in the next 30 days, higher than 38.8% of scored vulnerabilities.

Timeline

1. 13-05-2026
   PublishedVulnerability first disclosed.
2. 13-05-2026
   Last modifiedVulnerability information updated.

Description

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) to terminate.  Note: Software versions which have reached End of Technical Support (EoTS) are not evaluated.

• CWE-416Use After FreeThe product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory "belongs" to the code that operates on the new pointer.