CVE-2026-89658

A flaw was found in the Linux kernel's Network File System Daemon (NFSD). During NFSv4.0 revoked-state cleanup, a race condition can occur where a client's state identifier (stateid) reference does not properly prevent the client from being prematurely freed while still in use. This use-after-free vulnerability could allow a remote attacker to cause a denial of service (DoS) or potentially execute arbitrary code on the affected system.

A race in NFSD NFSv4.0 revoked state cleanup can cause a client use-after-free because nfs40_clean_admin_revoked takes a stateid reference but does not pin the owning client before dropping the global client lock. A concurrent client teardown can free the client while nfsd4_drop_revoked_stid still dereferences s sc_client and its cl_lock, creating a kernel memory safety issue. For the CVSS the PR:L value is used for the paranoid score because reliable triggering may require local access to NFSD control plane operations, but such access can be delegated to a reduced service account, container root, or restricted administrator rather than full host root in some deployments. The attack is not directly network reachable as a packet only trigger based on the patch context, although the affected NFSv4.0 state belongs to network clients. Impact is at least local denial of service via kernel crash and in worst case may allow confidentiality and integrity impact due to use-after-free memory corruption, so it should be reviewed manually.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.

Mitigation for this issue is either not available or the currently available options don't meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base or stability.