SB20260720246 - Use-after-free in Linux kernel handshake

Description

This security bulletin contains information about 1 vulnerability.

1) Use-after-free (CVE-ID: CVE-2026-63979)

CWE-ID: CWE-416 - Use After Free

CVSSv4: 6.8 [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]

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

The vulnerability exists due to a use-after-free in the net/handshake accept-side request handling code when processing queued handshake requests during concurrent cancellation. A local user can trigger a race condition to cause a denial of service.

The issue occurs because the accept side dereferences req->hr_sk->sk_socket->file after the request is removed from the pending list, while a concurrent cancellation path can release sock->file, clear sk_socket, or free the associated struct socket.

Remediation

Install update from vendor's website.

References

• https://git.kernel.org/stable/c/c06876d4fac38f35820946ee3b1be7d7da799cd4
• https://git.kernel.org/stable/c/f4251190e58b209999c1ba9e6d2976136a1be055