Out-of-bounds read in Linux kernel - CVE-2026-23327

Detailed vulnerability description

The vulnerability allows a local user to cause a denial of service, disclose sensitive information, and potentially execute arbitrary code.

The vulnerability exists due to improper input validation in the CXL mailbox command handler when processing user-supplied payloads. A local user can send a specially crafted raw mailbox command with an undersized payload to trigger an out-of-bounds read in the kernel, leading to memory disclosure, system crash, or potential code execution.

The issue specifically occurs in the cxl_payload_from_user_allowed() function, where the payload size is not validated before accessing its contents, resulting in a slab-out-of-bounds read during UUID comparison.

How to mitigate CVE-2026-23327

Sources

• https://git.kernel.org/stable/c/60b5d1f68338aff2c5af0113f04aefa7169c50c2
• https://git.kernel.org/stable/c/7c8a7b7f063b7e7ae9bba4cbaa14a5d2fe3a55e1