CVE-2026-31663 Linux CVE debrief

Who should care

System administrators and security teams responsible for Linux kernel-based systems should be aware of this vulnerability. Given its HIGH severity and potential for local privilege escalation, defenders should prioritize patching or mitigating this issue, especially in environments where local access is not tightly controlled or where there are services exposed to untrusted users.

Technical summary

The vulnerability is located in the xfrm (IPsec) component of the Linux kernel. Specifically, it involves the handling of device references during the asynchronous completion of crypto operations. When xfrm_input_resume() is called after async crypto completes, it immediately drops the device reference with dev_put(). However, the skb->dev pointer is used later in NF_HOOK and its okfn, which can lead to a use-after-free scenario if the device has been torn down. This issue can be exploited by local attackers to potentially escalate privileges or disrupt service.

Defensive priority

High priority due to potential for local privilege escalation and HIGH CVSS score.

Recommended defensive actions

• Inventory Linux kernel versions to identify affected systems.
• Review official Linux kernel advisories and patches for CVE-2026-31663.
• Apply patches or updates provided by Linux distributions to address the vulnerability.
• Implement compensating controls such as restricting local access to sensitive systems.
• Monitor system logs for suspicious activity indicative of exploitation attempts.

Evidence notes

The primary evidence for this vulnerability comes from the NVD CVE record and associated Linux kernel patches. The vulnerability affects multiple versions of the Linux kernel, from version 3.2.100 up to but not including 3.3, and various other ranges including 4.14.24 to 4.15, 4.15.1 to 6.18.23, and 6.19 to 6.19.13. Specific patches have been provided in the Linux kernel stable trees to address this issue.

Official resources