CVE-2026-64380 smb: client: harden POSIX SID length parsing
A missing boundary check in the Linux kernel SMB client allows reading out-of-bounds memory, potentially causing a denial of service.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-64380?
CVE-2026-64380 is a high-severity vulnerability in Linux kernel, published on 25 Jul 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
In the Linux kernel, the following vulnerability has been resolved:
smb: client: harden POSIX SID length parsing
posix_info_sid_size() reads sid[1] to obtain the subauthority count, but its existing boundary check still accepts buffers with only one remaining byte. Require two bytes before reading sid[1] so all client paths that reuse the helper reject truncated POSIX SIDs safely.
Weakness: CWE-125
Which versions are affected by CVE-2026-64380?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2026-64380?
Apply the vendor's patch.
Is CVE-2026-64380 being exploited?
There is no known exploitation of CVE-2026-64380 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as AZL-93854, BELL-CVE-2026-64380, DEBIAN-CVE-2026-64380, GHSA-86gc-pxpc-4p5h, ROOT-OS-DEBIAN-12-CVE-2026-64380, ROOT-OS-UBUNTU-2204-CVE-2026-64380 and 1 more.