SB20260502136 - Use-after-free in Linux kernel smb server

Description

This security bulletin contains information about 1 vulnerability.

1) Use-after-free (CVE-ID: CVE-2026-31718)

CWE-ID: CWE-416 - Use After Free

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

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

The vulnerability exists due to a use-after-free in __ksmbd_close_fd() when processing durable file handles that survive session disconnect and are later timed out by the durable scavenger. A remote user can trigger session disconnect without SMB2_LOGOFF and cause lock cleanup to access a freed connection object to cause a denial of service.

The issue occurs when a durable file handle is preserved for later reconnection and byte-range locks remain associated with the old connection.

Remediation

Install update from vendor's website.

References

• https://git.kernel.org/stable/c/235e32320a470fcd3998fb3774f2290a0eb302a1
• https://git.kernel.org/stable/c/3d6682726c2d3a46d31dae88b8166786b09b03ad
• https://git.kernel.org/stable/c/b34fc42cfe922e551f7a27d3ac3bb016e41d7dd9
• https://git.kernel.org/stable/c/e33c65f011980b4ad4abfd93585ec2079856368f