In the Linux kernel, the following vulnerability has been resolved: security/keys: fix missed RCU read section on lookup Nicholas Carlini reports… (CVE-2026-64015)

CVE-2026-64015 is a vulnerability in the Linux kernel's security/keys subsystem where the keyring code calls assoc_array_find() in find_key_to_update() without holding the required RCU read lock. This improper synchronization can cause lifetime issues in persistent key handling, potentially leading to system compromise. The vulnerability was fixed by adding the appropriate RCU locking. The issue affects multiple kernel versions prior to 6.8.0-1067.75 and 7.0.0-28.28 series among others. The fix is included in updated Linux kernel packages distributed by Ubuntu and other vendors.

The vulnerability allows a local attacker with limited privileges to exploit improper synchronization in the keyring subsystem, potentially leading to privilege escalation with high impact on confidentiality, integrity, and availability. The CVSS 3.1 score is 7.8 (high), reflecting local attack vector with low complexity, no user interaction, and full impact on confidentiality, integrity, and availability. No active exploitation has been reported.

A patch is available and has been released by Linux kernel maintainers and Ubuntu. Users should apply the updated kernel packages as provided by their distribution and reboot the system to activate the fixes. Due to an ABI change, recompilation and reinstallation of third-party kernel modules may be required. Follow vendor instructions for updating to the fixed versions to fully mitigate the vulnerability.