CVE-2026-89706

A flaw was found in the Linux kernel's nfsd component. When an asynchronous (async) copy writeback operation fails, the server's write verifier is not properly reset. This can lead to a client incorrectly assuming that data has been made durable, resulting in the silent loss of data that was intended to be copied.

An NFSd async COPY durability flaw can occur when post copy writeback or fsync reports an error but the server write verifier is not rotated. A client receives NFS_UNSTABLE via CB_OFFLOAD and then sends COMMIT, but the unchanged verifier can make the client conclude that failed writeback data is durable. For the CVSS the PR:L is used because the attacker typically needs authenticated NFS client access and permissions on an exported filesystem rather than only unauthenticated network reachability. The issue is network reachable through NFSv4.2 async COPY but practical triggering also depends on a server side writeback failure such as storage or filesystem error conditions. Impact is primarily integrity loss through silent data loss or false durability confirmation. There is no evidence of memory corruption, information disclosure, kernel crash, or privilege escalation.

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.