Improper input validation in Linux kernel - CVE-2026-64257
Published: July 27, 2026
Vulnerability identifier: #VU139731
CSH Severity: Medium
CVSS v4: 6.9 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N]
CVE-ID: CVE-2026-64257
CWE-ID: CWE-20
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vulnerability details
The vulnerability allows a remote attacker to cause a denial of service.
The vulnerability exists due to improper input validation in __smb2_calc_size() and smb2_check_message() when processing crafted SMB2 responses. A remote attacker can send a specially crafted SMB2 response with overlapping data areas to cause a denial of service.
The issue occurs because an overlapping data area can be misclassified as having no data area, allowing an invalid response to qualify for a length compatibility exception.
Affected software
Linux kernel
How to mitigate CVE-2026-64257
Install security update from vendor's repository.
Linux kernel - update to 7.0 rc3
External References
- https://git.kernel.org/stable/c/36bfa52459e45c0d5b668de2f1c91f6dc5c67775
- https://git.kernel.org/stable/c/445ece263131780dee273d727a4d6f11934feec7
- https://git.kernel.org/stable/c/4a9d2657d3e05f6ed09c148cb127b4e58702275f
- https://git.kernel.org/stable/c/57cba95f0e97c6f6e45e6731da30aff091bd7460
- https://git.kernel.org/stable/c/8986c932905ea508d66da421eb2eb6e676ace1fe
- https://git.kernel.org/stable/c/fdafa1e68dc75045b7b617e6e7d2854950804d83