CVE-2026-89706
Description
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.
Statement
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.
Mitigation
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.
Common Vulnerability Scoring System (CVSS) Score Details
Info alert:Important note
CVSS scores for open source components depend on vendor-specific factors (e.g. version or build chain). Therefore, Red Hat's score and impact rating can be different from NVD and other vendors. Red Hat remains the authoritative CVE Naming Authority (CNA) source for its products and services (see Red Hat classifications).
The following CVSS metrics and score provided are preliminary and subject to review.
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 5.5 | N/A | 7.5 |
| Attack Vector | Local | N/A | Network |
| Attack Complexity | Low | N/A | Low |
| Privileges Required | Low | N/A | None |
| User Interaction | None | N/A | None |
| Scope | Unchanged | N/A | Unchanged |
| Confidentiality | None | N/A | None |
| Integrity Impact | None | N/A | High |
| Availability Impact | High | N/A | None |
Vector
Red Hat: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
cve.org: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
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