SB20260727179 - Incorrect Implementation of Authentication Algorithm in Linux kernel smb server

Description

This security bulletin contains information about 1 vulnerability.

1) Incorrect Implementation of Authentication Algorithm (CVE-ID: CVE-2026-64389)

CWE-ID: CWE-303 - Incorrect Implementation of Authentication Algorithm

CVSSv4: 5.3 [CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N]

The vulnerability allows a remote user to modify session key material.

The vulnerability exists due to improper authentication logic in ksmbd NTLMv2 authentication handling when processing SMB3 multichannel binding session setup requests with KEY_XCH. A remote user can send a binding session setup with a bad NT proof and KEY_XCH to modify session key material.

The issue occurs on an existing session because the failed authentication path does not expire binding sessions.

Remediation

Install update from vendor's website.

References

• https://git.kernel.org/stable/c/89ca7756d5566ba636bb9092cdbe57dab095e136
• https://git.kernel.org/stable/c/954d196bebb2b50151cb96454c72dc113b2af1ac
• https://git.kernel.org/stable/c/b56400364aed5c34d6e1a0b493081290a5328a9c