CVE-2026-74343 kernfs: fix xattr race condition with multiple superblocks
A race condition in the Linux kernel's kernfs allows concurrent xattr modifications to corrupt shared data, potentially leading to data modification or denial of service.
- 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-2026-74343?
CVE-2026-74343 is a high-severity vulnerability in Linux, published on 15 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:
kernfs: fix xattr race condition with multiple superblocks
Multiple superblocks with different namespaces can share the same kernfs_node when kernfs_test_super() finds a matching root but different namespace. This means multiple inodes from different superblocks can reference the same kernfs_node->iattr->xattrs structure.
The VFS layer only holds per-inode locks during xattr operations, which is insufficient to serialize concurrent xattr modifications on the shared kernfs_node. This can lead to race conditions in simple_xattr_set() where the lookup->replace/remove sequence is not atomic with respect to operations from other superblocks.
Fix this by protecting xattr operations with the existing hashed kernfs_locks->open_file_mutex[] array, which is already used to protect per-node open file data. The hashed mutex array provides scalable per-node serialization (scaled by CPU count, up to 1024 locks on 32+ CPU systems) with zero memory overhead.
Changes: - Rename open_file_mutex[] to node_mutex[] to reflect dual purpose - Add kernfs_node_lock_ptr() and kernfs_node_lock() helpers - Protect simple_xattr_set() calls in kernfs_xattr_set() and kernfs_vfs_user_xattr_set() with the hashed mutex - Update file.c to use new helpers via compatibility wrappers - Update documentation to explain the extended lock usage
Which versions are affected by CVE-2026-74343?
How do I fix CVE-2026-74343?
Apply the vendor's patch.
Is CVE-2026-74343 being exploited?
There is no known exploitation of CVE-2026-74343 in the wild and no public exploit code.
Sources
Also known as DEBIAN-CVE-2026-74343, GHSA-rxfr-7h9v-g4vx, UBUNTU-CVE-2026-74343.