CVE-2026-53393 nfsd: reset write verifier on deferred writeback errors

What is CVE-2026-53393?

CVE-2026-53393 is a medium-severity vulnerability in Linux kernel, published on 19 Jul 2026.

Official 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.

Which versions are affected by CVE-2026-53393?

It affects 1 product.

Products include Linux kernel.

How do I fix CVE-2026-53393?

Upgrade to a fixed version.

Is CVE-2026-53393 being exploited?

There is no known exploitation of CVE-2026-53393 in the wild and no public exploit code.

Other vulnerabilities in Linux kernel

• CVE-2026-53266 Linux Kernel Out-of-Bounds Write Exploited High 8.8
• CVE-2013-6282 Linux Kernel Improper Input Validation Exploited High 8.8
• CVE-2022-0185 Linux Kernel Heap-Based Buffer Overflow Exploited High 8.4
• CVE-2013-2094 Linux Kernel Privilege Escalation Exploited High 8.4
• CVE-2026-53362 Linux Kernel Unspecified Exploited High 7.8

All Linux kernel vulnerabilities

Sources

• CVE record
• NVD
• OSV
• GitHub advisory
• How this page is made

Also known as AZL-92600, BELL-CVE-2026-53393, DEBIAN-CVE-2026-53393, GHSA-wm3m-j54f-523v, ROOT-OS-DEBIAN-11-CVE-2026-53393, ROOT-OS-DEBIAN-12-CVE-2026-53393 and 2 more.