CVE-2026-68457 ksmbd: use opener credentials for FSCTL mutations
Attackers can bypass permission checks on SMB file operations by exploiting credential mishandling in the ksmbd kernel module.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-68457?
CVE-2026-68457 is a critical vulnerability in Linux, published on 15 Aug 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:
ksmbd: use opener credentials for FSCTL mutations
SET_SPARSE, SET_ZERO_DATA and SET_COMPRESSION operate on an open SMB handle but call VFS xattr, fallocate or fileattr helpers with the current ksmbd worker credentials. Those helpers can revalidate inode permissions, ownership and LSM policy independently of the SMB handle access mask.
Run each operation with the credentials captured in the target file when the handle was opened. Keep credential handling local to these single-file FSCTLs rather than applying session credentials to the complete IOCTL handler, which also contains handle-less and multi-handle operations.
Which versions are affected by CVE-2026-68457?
How do I fix CVE-2026-68457?
Apply the vendor's patch.
Is CVE-2026-68457 being exploited?
There is no known exploitation of CVE-2026-68457 in the wild and no public exploit code.
Sources
Also known as BELL-CVE-2026-68457, DEBIAN-CVE-2026-68457, GHSA-j57w-wqmx-67hp, UBUNTU-CVE-2026-68457.