CVE-2026-41956: DoS in F5 BIG-IP via UDP Classification

Successful exploitation of CVE-2026-41956 allows an attacker to induce a denial-of-service condition on the affected F5 BIG-IP system. This results in the Traffic Management Microkernel (TMM) terminating, effectively halting traffic processing and rendering the virtual server unavailable. The impact can range from temporary service outages to prolonged disruptions, potentially affecting critical applications and services dependent on the BIG-IP infrastructure. The blast radius is limited to the specific UDP virtual server and its associated services, but widespread impact is possible if the affected BIG-IP device handles high-volume traffic or is a critical component of the network infrastructure. While no public exploits are currently available, the DoS nature of the vulnerability makes it a potential target for opportunistic attacks.

1. Gereserveerd2026-04-30
2. Gepubliceerd2026-05-13

The primary mitigation for CVE-2026-41956 is to upgrade F5 BIG-IP to version 17.5.1.4 or later, which contains the fix. If immediate upgrade is not feasible, consider implementing temporary workarounds. Review and restrict access to UDP virtual servers with classification profiles, limiting exposure to untrusted sources. Implement rate limiting on UDP traffic to mitigate the impact of potential DoS attacks. Monitor BIG-IP system logs for unusual traffic patterns or error messages related to TMM crashes. After upgrading, confirm the fix by sending a test request to the affected UDP virtual server and verifying that TMM remains stable.