SB2026072130 - Out-of-bounds write in Linux kernel sched

Description

This security bulletin contains information about 1 vulnerability.

1) Out-of-bounds write (CVE-ID: CVE-2026-63799)

CWE-ID: CWE-787 - Out-of-bounds write

CVSSv4: 5.8 [CVSS:4.0/AV:L/AC:L/AT:P/PR:L/UI:N/VC:N/VI:H/VA:H/SC:N/SI:N/SA:N]

The vulnerability allows a local user to corrupt kernel memory.

The vulnerability exists due to an out-of-bounds write in mm_cid_schedout() via mm_cid_fixup_cpus_to_tasks() when handling a task with MM_CID_UNSET in the per-CPU to per-task fixup path. A local user can trigger task state transitions such as fork() or execve() during this window to corrupt kernel memory.

The issue occurs only in per-CPU CID mode during the window before the task's next schedule-in assigns a real CID, and the resulting corruption is a deterministic single-bit clear at a fixed offset rather than an arbitrary write.

Remediation

Install update from vendor's website.

References

• https://git.kernel.org/stable/c/8d32856fb72ba976d9c87ba405fd17e80419934c
• https://git.kernel.org/stable/c/de3ab9bd3133899efb92e4cd05ba4203e58fc0a3