SB20260507233 - Race condition in Linux kernel io_uring

Description

This security bulletin contains information about 1 vulnerability.

1) Race condition (CVE-ID: CVE-2026-43121)

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

CVSSv4: CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:U/U:Clear

The vulnerability allows a local user to cause a denial of service.

The vulnerability exists due to a race condition leading to double free and out-of-bounds write in io_uring zcrx niov freelist handling when concurrent scrub and refill paths manipulate user_refs. A local user can trigger concurrent operations to cause a denial of service.

The issue occurs on SMP systems due to unsynchronized access to the same reference counter.

Remediation

Install update from vendor's website.

References

• https://git.kernel.org/stable/c/003049b1c4fb8aabb93febb7d1e49004f6ad653b
• https://git.kernel.org/stable/c/485dc691257b96e6d3bdc25b0eff2daadcc5c46c
• https://git.kernel.org/stable/c/a94f096e28bfc7975163a6b80f1c8f323efe317a