# CVE-2026-80899: erofs: remove fscache backend entirely

> Removal of the deprecated EROFS fscache backend in the Linux kernel to eliminate implementation issues and dependencies.

- **Severity:** Not scored
- **Exploited in the wild:** Not known
- **Login needed:** Not stated
- **Attackable:** Not stated
- **Victim action needed:** Not stated
- **Fix available:** Yes
- **Published:** 4 Sep 2026
- **Updated:** 7 Sep 2026
- **Also known as:** AZL-99582, BELL-CVE-2026-80899, DEBIAN-CVE-2026-80899, GHSA-gh58-fmwq-66r3, UBUNTU-CVE-2026-80899

## What is CVE-2026-80899?

CVE-2026-80899 is a vulnerability in Linux, published on 4 Sep 2026. 

### Official description

In the Linux kernel, the following vulnerability has been resolved:

erofs: remove fscache backend entirely

EROFS over fscache was introduced to provide image lazy pulling
functionality. After the feature landed, the fscache subsystem made
netfs a new hard dependency, which is unexpected for a local filesystem
and has an kernel-defined caching hierarchy which could be inflexible
compared to the fanotify pre-content hooks. Therefore, this feature has
been deprecated for almost two years.

As EROFS file-backed mounts and fanotify pre-content hooks both upstream
for a while and already providing equivalent functionality (erofs-utils
has supported fanotify pre-content hooks), let's remove the fscache
backend now.

The main application of this feature is Nydus [1], and they plan to move
to use fanotify pre-content hooks in the near future too.

I hope this patch can be merged into Linux 7.2, which is also motivated
by newly found implementation issues [2][3] that are not worth
investigating given the deprecation and limited development resources.
The associated fscache/cachefiles cleanup patch will follow separately
through the vfs tree (netfs) later: it seems fine since the codebase is
isolated by CONFIG_CACHEFILES_ONDEMAND.

[1] https://github.com/dragonflyoss/nydus/blob/v2.1.0/docs/nydus-fscache.md
[2] https://github.com/dragonflyoss/nydus/pull/1824
[3] https://lore.kernel.org/r/20260619135800.1594811-1-michael.bommarito@gmail.com

## Which versions are affected by CVE-2026-80899?


## How do I fix CVE-2026-80899?

Apply the vendor's patch.

## Is CVE-2026-80899 being exploited?

There is no known exploitation of CVE-2026-80899 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-80899 and fix it if it is affected.

What it is: CVE-2026-80899 is a vulnerability in Linux, published on 4 Sep 2026. 
Exploitation: There is no known exploitation of CVE-2026-80899 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-2026-80899/ (Markdown: https://insights.sbomify.com/CVE-2026-80899/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-80899
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-80899
- OSV: https://osv.dev/vulnerability/CVE-2026-80899

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-80899/
Summaries are generated and may contain mistakes; the official description above is the record.