CVE-2026-53393
Received Received - Intake

Write Verifier Reset Failure in Linux Kernel NFS Server

Publication date: 2026-07-19

Last updated on: 2026-07-19

Assigner: kernel.org

Description
In the Linux kernel, the following vulnerability has been resolved: nfsd: reset write verifier on deferred writeback errors nfsd_vfs_write() and nfsd_commit() both call filemap_check_wb_err() to detect deferred writeback errors, but neither rotates the server's write verifier (nn->writeverf) when this check fails. Every other durable-storage-failure path in these functions calls commit_reset_write_verifier() before returning an error. The missing rotation means clients holding UNSTABLE write data under the current verifier will COMMIT, receive the unchanged verifier back, and conclude their data is durable — silently dropping data that failed writeback. This violates the UNSTABLE+COMMIT durability contract (RFC 1813 §3.3.7, RFC 8881 §18.32). Add commit_reset_write_verifier() calls at both filemap_check_wb_err() error sites, matching the pattern used by adjacent error paths in the same functions. The helper already filters -EAGAIN and -ESTALE internally, so the calls are unconditionally safe.

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Meta Information

Published
2026-07-19
Last Modified
2026-07-19
Generated
2026-07-20
AI Q&A
2026-07-19
EPSS Evaluated
N/A
NVD
CVE-2026-53393
EUVD
EUVD-2026-45515

Affected Vendors & Products

Showing 1 associated CPE
Vendor Product Version / Range
linux linux_kernel *

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Exploitability

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CWE ID Description
CWE-UNKNOWN

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Executive Summary

This vulnerability in the Linux kernel involves a missing reset of the write verifier when deferred writeback errors occur in NFS (Network File System) operations. Specifically, nfsd_vfs_write() and nfsd_commit() functions fail to rotate the server's write verifier when filemap_check_wb_err() detects writeback errors. This allows clients to incorrectly assume their data is durable after a COMMIT operation, potentially leading to silent data loss.

Detection Guidance

This vulnerability affects the Linux kernel's NFS server implementation. Detection requires checking kernel logs for NFS-related errors or verifying if the system is running a vulnerable kernel version. Commands like 'dmesg | grep nfsd' or 'journalctl -u nfs-server' may show related errors. However, specific detection commands are not provided in the given context.

Impact Analysis

If you use NFS for file storage, this vulnerability could cause data loss. Clients may believe their data is safely stored when it actually failed to write properly. This could lead to corruption or loss of critical files, especially in environments relying on NFS for shared storage.

Compliance Impact

This vulnerability could violate compliance requirements for data integrity and durability, such as those in GDPR (data protection) and HIPAA (healthcare data). If data is silently lost or corrupted due to the NFS write verifier issue, organizations may fail to meet regulatory obligations for data retention and integrity.

Mitigation Strategies

Immediate mitigation involves updating the Linux kernel to a patched version that includes the fix for this NFS write verifier issue. Check your distribution's security advisories for kernel updates and apply them promptly.

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