SB2026072146 - Always-Incorrect Control Flow Implementation in Linux kernel nfsd

Description

This security bulletin contains information about 1 vulnerability.

1) Always-Incorrect Control Flow Implementation (CVE-ID: CVE-2026-53393)

CWE-ID: CWE-670 - Always-Incorrect Control Flow Implementation

CVSSv4: 7.1 [CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N]

The vulnerability allows a remote user to cause silent data loss.

The vulnerability exists due to improper state management in nfsd_vfs_write() and nfsd_commit() when handling deferred writeback errors for UNSTABLE write data followed by COMMIT. A remote user can trigger writeback errors and then issue COMMIT operations to cause silent data loss.

The issue violates the UNSTABLE+COMMIT durability contract by returning an unchanged write verifier after failed writeback.

Remediation

Install update from vendor's website.

References

• https://git.kernel.org/stable/c/1dd664b39774a9c89b72de8e59bf9ef4b3aaff2e
• https://git.kernel.org/stable/c/2090b05803faab8a9fa62fbff871007862cac1b7
• https://git.kernel.org/stable/c/4367afc119c51e17a616f6908772b7e2c2c4013f
• https://git.kernel.org/stable/c/b027cca33c97354149fcc0ddeede4525c41093cd