Incorrect Implementation of Authentication Algorithm in Linux kernel - CVE-2026-64389
Published: July 27, 2026
Vulnerability identifier: #VU139576
CSH Severity: Low
CVSS v4: 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]
CVE-ID: CVE-2026-64389
CWE-ID: CWE-303
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vulnerability details
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.
Affected software
Linux kernel
How to mitigate CVE-2026-64389
Install security update from vendor's repository.
Linux kernel - update to 7.0 rc3