CVE-2026-68448 ovl: check access to copy_file_range source with src mounter creds
A local attacker can bypass read permission checks in overlayfs copy_file_range operations, potentially reading files they should not access.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-68448?
CVE-2026-68448 is a missing authorization vulnerability in Linux, published on 12 Aug 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
In the Linux kernel, the following vulnerability has been resolved:
ovl: check access to copy_file_range source with src mounter creds
Commit 5dae222a5ff0c ("vfs: allow copy_file_range to copy across devices") allowed filesystems that implement the copy_file_range() f_op to decide if they want to access cross-sb copy from/to the same fs type.
The same commit added checks to verify same sb copy for filesystems that implement ->copy_file_range() and do not support cross-sb copy at the time, namely, to ceph, fuse and nfs.
The two remaining fs which implement ->copy_file_range(), cifs and overlayfs started to support cross-sb copy from this time.
While overlayfs does support cross-sb copy when the two underlying files are on the same base fs, the copy operation on the two real files from two different overalyfs filesystems is performed with the mounter creds of the destination overlayfs and the read permission access hook for the source file was called with the wrong creds.
This could cause either deny of access to copy which would otherwise be allowed (e.g. with splice) or allow read access to file which would otherwise be denied.
Fix the latter case by explicitly verifying read access to source file with the source overlayfs mounter creds.
The former case remains a quirk of cross-sb overlayfs copy, but userspace could fall back to regular copy so no harm done.
Which versions are affected by CVE-2026-68448?
How do I fix CVE-2026-68448?
Apply the vendor's patch.
Upgrade, and check permissions on every request on the server, not only in the interface. More about Missing authorization.
Is CVE-2026-68448 being exploited?
There is no known exploitation of CVE-2026-68448 in the wild and no public exploit code.
Sources
Also known as AZL-95513, BELL-CVE-2026-68448, DEBIAN-CVE-2026-68448, GHSA-7vqh-66x8-88v7, UBUNTU-CVE-2026-68448.