CVE-2026-41218: CWE-416: Use After Free in F5 BIG-IP
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.
AI Analysis
Technical Summary
This vulnerability (CVE-2026-41218) is a use-after-free condition (CWE-416) in the F5 BIG-IP Traffic Management Microkernel (TMM) triggered by specific PEM iRules commands on a virtual server. When iRules containing commands such as CLASSIFICATION::, CLASSIFY::, PEM::, PSC::, and urlcatquery are used, certain undisclosed traffic can cause TMM to terminate unexpectedly. This results in a denial of service condition. The vulnerability affects multiple versions of BIG-IP, including 21.0.0, 17.5.0, 17.1.0, and 16.1.0. The CVSS v3.1 base score is 7.5, reflecting network attack vector, low attack complexity, no privileges or user interaction required, and impact limited to availability. There is no vendor advisory or patch information currently available, and no known exploits in the wild have been reported.
Potential Impact
Successful exploitation causes the Traffic Management Microkernel (TMM) to terminate, resulting in denial of service. There is no reported impact on confidentiality or integrity. The vulnerability can be triggered remotely without authentication or user interaction.
Mitigation Recommendations
Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. Until an official fix is available, consider avoiding the use of the affected iRules commands (CLASSIFICATION::, CLASSIFY::, PEM::, PSC::, and urlcatquery) on virtual servers if possible. Monitor vendor communications for updates on patches or mitigations.
CVE-2026-41218: CWE-416: Use After Free in F5 BIG-IP
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.
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
This vulnerability (CVE-2026-41218) is a use-after-free condition (CWE-416) in the F5 BIG-IP Traffic Management Microkernel (TMM) triggered by specific PEM iRules commands on a virtual server. When iRules containing commands such as CLASSIFICATION::, CLASSIFY::, PEM::, PSC::, and urlcatquery are used, certain undisclosed traffic can cause TMM to terminate unexpectedly. This results in a denial of service condition. The vulnerability affects multiple versions of BIG-IP, including 21.0.0, 17.5.0, 17.1.0, and 16.1.0. The CVSS v3.1 base score is 7.5, reflecting network attack vector, low attack complexity, no privileges or user interaction required, and impact limited to availability. There is no vendor advisory or patch information currently available, and no known exploits in the wild have been reported.
Potential Impact
Successful exploitation causes the Traffic Management Microkernel (TMM) to terminate, resulting in denial of service. There is no reported impact on confidentiality or integrity. The vulnerability can be triggered remotely without authentication or user interaction.
Mitigation Recommendations
Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. Until an official fix is available, consider avoiding the use of the affected iRules commands (CLASSIFICATION::, CLASSIFY::, PEM::, PSC::, and urlcatquery) on virtual servers if possible. Monitor vendor communications for updates on patches or mitigations.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- f5
- Date Reserved
- 2026-04-30T23:02:47.670Z
- Cvss Version
- 3.1
- State
- PUBLISHED
- Remediation Level
- null
Threat ID: 6a049711cbff5d8610dff661
Added to database: 5/13/2026, 3:21:53 PM
Last enriched: 5/13/2026, 3:53:19 PM
Last updated: 5/14/2026, 6:52:39 AM
Views: 2
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