In the Linux kernel, the following vulnerability has been resolved: nfsd: Reset write verifier when async COPY writeback fails Async COPY captures… (CVE-2026-89706)
A vulnerability in the Linux kernel's NFS server (nfsd) related to async COPY writeback failure handling has been resolved. The issue involved the write verifier not being reset when async COPY writeback fails, causing clients to incorrectly assume data durability. This violates the NFS protocol's durability contract and can lead to silent data loss. The fix rotates the write verifier upon writeback failure to ensure correct client behavior.
AI Analysis
Technical Summary
The Linux kernel's NFS server async COPY operation captures the write verifier at request time and reports it to the client after completion. If the async COPY writeback fails, the worker clears the committed flag and reports the write as unstable, but the server's write verifier is not rotated. Consequently, the client receives the same verifier value during COMMIT, mistakenly concluding the data is durable despite the failure. This breaks the NFS UNSTABLE+COMMIT durability contract as defined in RFC 7862 and RFC 8881. The patch rotates the write verifier at the writeback failure site, using a direct call to nfsd_reset_write_verifier(), ensuring clients correctly detect writeback failures and avoid silent data loss.
Potential Impact
Clients using NFS async COPY may silently lose data because they incorrectly believe the data is durable after a failed writeback. This undermines the durability guarantees of the NFS protocol, potentially causing data integrity issues for applications relying on NFS.
Mitigation Recommendations
A fix has been applied in the Linux kernel to rotate the write verifier when async COPY writeback fails, preventing clients from incorrectly assuming data durability. Users should update to a Linux kernel version that includes this fix. Patch status is not explicitly stated in the input; check the vendor advisory for the exact fixed versions and remediation guidance.
In the Linux kernel, the following vulnerability has been resolved: nfsd: Reset write verifier when async COPY writeback fails Async COPY captures… (CVE-2026-89706)
Description
A vulnerability in the Linux kernel's NFS server (nfsd) related to async COPY writeback failure handling has been resolved. The issue involved the write verifier not being reset when async COPY writeback fails, causing clients to incorrectly assume data durability. This violates the NFS protocol's durability contract and can lead to silent data loss. The fix rotates the write verifier upon writeback failure to ensure correct client behavior.
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
The Linux kernel's NFS server async COPY operation captures the write verifier at request time and reports it to the client after completion. If the async COPY writeback fails, the worker clears the committed flag and reports the write as unstable, but the server's write verifier is not rotated. Consequently, the client receives the same verifier value during COMMIT, mistakenly concluding the data is durable despite the failure. This breaks the NFS UNSTABLE+COMMIT durability contract as defined in RFC 7862 and RFC 8881. The patch rotates the write verifier at the writeback failure site, using a direct call to nfsd_reset_write_verifier(), ensuring clients correctly detect writeback failures and avoid silent data loss.
Potential Impact
Clients using NFS async COPY may silently lose data because they incorrectly believe the data is durable after a failed writeback. This undermines the durability guarantees of the NFS protocol, potentially causing data integrity issues for applications relying on NFS.
Mitigation Recommendations
A fix has been applied in the Linux kernel to rotate the write verifier when async COPY writeback fails, preventing clients from incorrectly assuming data durability. Users should update to a Linux kernel version that includes this fix. Patch status is not explicitly stated in the input; check the vendor advisory for the exact fixed versions and remediation guidance.
Technical Details
- Gcve Source
- db.gcve.eu
- Osv Id
- GHSA-gfmq-vxg4-w276
- Osv Schema Version
- 1.4.0
- Aliases
- ["CVE-2026-89706"]
Threat ID: 6aa49ffd55bf5e2cf5a865ec
Added to database: 09/12/2026, 00:42:37 UTC
Last enriched: 09/12/2026, 00:52:29 UTC
Last updated: 09/12/2026, 00:52:29 UTC
Views: 2
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