Out-of-bounds write in Linux kernel - CVE-2026-63996

Detailed vulnerability description

The vulnerability allows an attacker with physical access to cause a denial of service.

The vulnerability exists due to out-of-bounds write in cmis_cdb_process_reply() when processing a crafted CDB reply from an SFP module. An attacker with physical access can provide a malicious SFP module that returns an overlong reply to cause a denial of service.

The issue can be triggered by a malicious module, and the advisory notes that buggy hardware or corrupted reads may also reach the vulnerable condition.

How to mitigate CVE-2026-63996

Sources

• https://git.kernel.org/stable/c/2f818cc98fd2c63a08239cb48995f6c3bfe9d9b3
• https://git.kernel.org/stable/c/4d42fb88ec61f2e98c33a9e3a2de371d5edbc6b1
• https://git.kernel.org/stable/c/6c3f999a9d1338c6c89a9ff4549eafe72bc2e7b1
• https://git.kernel.org/stable/c/eb5dcd740cd7fa27bc2caeff2d28ef28e93ff4d3