CVE-2026-43350 smb: client: require a full NFS mode SID before reading mode bits
A malicious SMB server can trigger an out-of-bounds read in the Linux kernel SMB client, potentially leaking memory or causing a crash.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- A user has to click or open something
- Fix
- Available
What is CVE-2026-43350?
CVE-2026-43350 is a high-severity memory corruption vulnerability in Linux kernel, published on 8 May 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Official description
In the Linux kernel, the following vulnerability has been resolved:
smb: client: require a full NFS mode SID before reading mode bits
parse_dacl() treats an ACE SID matching sid_unix_NFS_mode as an NFS mode SID and reads sid.sub_auth[2] to recover the mode bits.
That assumes the ACE carries three subauthorities, but compare_sids() only compares min(a, b) subauthorities. A malicious server can return an ACE with num_subauth = 2 and sub_auth[] = {88, 3}, which still matches sid_unix_NFS_mode and then drives the sub_auth[2] read four bytes past the end of the ACE.
Require num_subauth >= 3 before treating the ACE as an NFS mode SID. This keeps the fix local to the special-SID mode path without changing compare_sids() semantics for the rest of cifsacl.
Weakness: CWE-125
Which versions are affected by CVE-2026-43350?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2026-43350?
Apply the vendor's patch.
Upgrade to the fixed version. Memory-safe languages, compiler hardening and fuzzing prevent most new cases. More about Memory corruption.
Is CVE-2026-43350 being exploited?
There is no known exploitation of CVE-2026-43350 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as BELL-CVE-2026-43350, DEBIAN-CVE-2026-43350, GHSA-xvvm-359f-6vgc, ROOT-OS-DEBIAN-11-CVE-2026-43350, ROOT-OS-DEBIAN-12-CVE-2026-43350, ROOT-OS-UBUNTU-2204-CVE-2026-43350 and 2 more.