The Linux kernel fuse-uring subsystem had a vulnerability where, when io_uring delivered task work with cancellation set, the function fuse_uring_send_in_task() took a cancel branch that assigned an error code but did not properly discharge the owning reference to the fuse_req structure. This caused the fuse_req to remain linked in internal processing lists and never properly ended, potentially leading to resource leaks or other stability issues. The vulnerability affects Linux kernel versions prior to 7.0.0-31.31 and related variants. Ubuntu has released patched kernel versions to address this issue as part of broader Linux kernel security updates. The vulnerability has a CVSS 3.1 base score of 5.5 (medium severity) with local attack vector, low complexity, low privileges required, no user interaction, and impacts availability.

The vulnerability can cause improper resource management in the fuse-uring subsystem of the Linux kernel, potentially leading to denial of service or system instability due to unreleased references. There is no indication of confidentiality or integrity impact. The CVSS score of 5.5 reflects a medium severity with an impact primarily on availability. No known exploits are reported in the wild.

A patch is available and has been released by Ubuntu in updated Linux kernel packages. Users should apply the official kernel updates for their respective Ubuntu releases and reboot their systems to ensure the fixes take effect. Due to an ABI change, recompilation and reinstallation of third-party kernel modules may be required. Follow the vendor advisory instructions for updating to the fixed kernel versions.