CVE-2026-41227 F5 CVE debrief

Who should care

Security teams responsible for F5 BIG-IP products, particularly those using Advanced Web Application Firewall, Application Security Manager, and DDoS Hybrid Defender, should be aware of this vulnerability. Additionally, organizations that rely on these products for web application security and traffic management should prioritize patching and mitigation. CVE-2026-41227's high severity and potential for denial-of-service impact make it a critical concern.

Technical summary

CVE-2026-41227 is a vulnerability in F5 BIG-IP Advanced Web Application Firewall that can lead to increased memory consumption and termination of the Traffic Management Microkernel (TMM) process. The issue arises from undisclosed traffic on an HTTP/2 virtual server with Layer 7 DoS Protection configured. Affected products include BIG-IP Advanced Web Application Firewall, BIG-IP Application Security Manager, and BIG-IP DDoS Hybrid Defender, across various version ranges. The vulnerability's CVSS vector is CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X. F5 has provided a vendor advisory for mitigation.

Defensive priority

High priority should be given to patching and mitigating CVE-2026-41227 due to its high severity and potential for denial-of-service impact. Security teams should immediately review affected F5 BIG-IP products and apply necessary patches or workarounds.

Recommended defensive actions

• Review and apply F5's vendor advisory (K000158979) for mitigation guidance.
• Immediately patch affected F5 BIG-IP products, including BIG-IP Advanced Web Application Firewall, BIG-IP Application Security Manager, and BIG-IP DDoS Hybrid Defender.
• Conduct thorough inventory checks to identify and prioritize affected systems.
• Implement compensating controls, such as enhanced monitoring and traffic filtering, until patches can be applied.
• Track and verify F5's remediation workflow for this vulnerability.

Evidence notes

The CVE-2026-41227 record was obtained from the official CVE database and the National Vulnerability Database (NVD). The vulnerability affects multiple F5 BIG-IP products across various version ranges. F5 has provided a vendor advisory for mitigation. The CVSS score of 8.7 indicates high severity. The CVE was published on May 13, 2026, and last modified on June 24, 2026.

Official resources