Improper access control in Linux kernel - CVE-2026-53383
Published: July 21, 2026
Vulnerability identifier: #VU138877
CSH Severity: Medium
CVSS v4: 8.7 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N]
CVE-ID: CVE-2026-53383
CWE-ID: CWE-284
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 access control in smb2_check_user_session() and the ksmbd compound request handling path when processing a crafted compound SMB request with a non-valid session. A remote attacker can send a specially crafted compound request to cause a denial of service.
By using SESSION_SETUP as the first compound operation and a related TREE_CONNECT request with SessionId set to ULLONG_MAX as the second operation, an in-progress session can reach a NULL pointer dereference because sess->user remains NULL.
Affected software
Linux kernel
How to mitigate CVE-2026-53383
Install security update from vendor's repository.
Linux kernel - update to 7.0 rc3
External References
- https://git.kernel.org/stable/c/06e1f05a1dbe8bbd054c0927b17fc0a61cc8bef7
- https://git.kernel.org/stable/c/25ff12b82a376ff5c4583102a63d2456a6b9ebb9
- https://git.kernel.org/stable/c/5f983b864d3d473ac533b2f4f44a1bbe5dcbccf4
- https://git.kernel.org/stable/c/609ca17d869d04ba249e32cdcbf13c0b1c66f43c
- https://git.kernel.org/stable/c/7cad3ceaf679c55bc9946685dacafce78ce6b51a
- https://git.kernel.org/stable/c/8f0302fb691537d33ec8f668565257ea9d340ffe
- https://git.kernel.org/stable/c/d2bbbb6c55812220fee5d801c275cc267ea3cbeb
- https://git.kernel.org/stable/c/fc578523a72cb8b329d32070b95898e81613cc3f