CVE-2026-72377 afs: Remove setting of AS_RELEASE_ALWAYS for symlinks and mountpoints
A null pointer dereference in the Linux kernel AFS filesystem can cause a denial of service when accessing symlinks or mountpoints with fscache enabled.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-72377?
CVE-2026-72377 is a 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:
afs: Remove setting of AS_RELEASE_ALWAYS for symlinks and mountpoints
Regular AFS files correctly use afs_file_aops which have release_folio set as netfs_release_folio, so AS_RELEASE_ALWAYS is valid for them when fscache is enabled (set via afs_vnode_set_cache()). Symlinks and mountpoints in AFS use afs_dir_aops, which does not provide a release_folio callback. However, afs_apply_status() unconditionally calls mapping_set_release_always() for these.
In such case when memory management code attempts to release folios, filemap_release_folio() checks folio_needs_release() which returns true due to AS_RELEASE_ALWAYS being set. Since there is no release_folio callback, it falls through to try_to_free_buffers(), which at present expects buffer_heads to be not null. For symlinks and mountpoints without buffer_heads, this causes pointer dereference.
[dh: Added more bits that were missed]
Which versions are affected by CVE-2026-72377?
How do I fix CVE-2026-72377?
Apply the vendor's patch.
Is CVE-2026-72377 being exploited?
There is no known exploitation of CVE-2026-72377 in the wild and no public exploit code.
Sources
Also known as BELL-CVE-2026-72377, DEBIAN-CVE-2026-72377, GHSA-jw6q-qfr2-5f75, UBUNTU-CVE-2026-72377.