SB20261029207 - Race condition in Linux kernel smb client

Description

This security bulletin contains information about 1 vulnerability.

1) Race condition (CVE-ID: CVE-2026-99111)

CWE-ID: CWE-362 - Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition')

CVSSv4: 2 [CVSS:4.0/AV:L/AC:L/AT:P/PR:L/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N]

The vulnerability allows a local user to corrupt file data on an SMB share.

The vulnerability exists due to a race condition in the Linux kernel SMB client's cifs_do_truncate() function when processing concurrent buffered writes and O_TRUNC operations without holding the required locks throughout the flush-truncate-resize sequence. A local user can trigger a buffered write after dirty pages are flushed but before local truncation to cause newly dirtied pages to be silently discarded by cifs_setsize() and truncate_pagecache(), resulting in file data corruption.

Remediation

Install update from vendor's website.

References

• https://git.kernel.org/stable/c/4d143608a0445443a85c9b29f4c9f8e63d5dbfc9
• https://git.kernel.org/stable/c/a8603b52b39f520ea8a34def74c23fba87396d3e
• https://git.kernel.org/stable/c/ffa66fdc7d35b890606767c4d2c7ac26b4d90a99