# 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.

- **Severity:** Not scored
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 15 Aug 2026
- **Updated:** 17 Aug 2026
- **Also known as:** BELL-CVE-2026-72377, DEBIAN-CVE-2026-72377, GHSA-jw6q-qfr2-5f75, UBUNTU-CVE-2026-72377

## 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.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-72377 and fix it if it is affected.

What it is: 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.
Exploitation: There is no known exploitation of CVE-2026-72377 in the wild and no public exploit code.

Affected product: Linux. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-72377/ (Markdown: https://insights.sbomify.com/CVE-2026-72377/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-72377
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-72377
- OSV: https://osv.dev/vulnerability/CVE-2026-72377

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-72377/
Summaries are generated and may contain mistakes; the official description above is the record.