# CVE-2026-74349: ocfs2: reject FITRIM ranges shorter than a cluster

> An integer underflow in the OCFS2 filesystem allows a local attacker to cause a denial of service by triggering a FITRIM operation with a specific range size.

- **Severity:** High 7.1 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:H`)
- **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:** Yes
- **Published:** 15 Aug 2026
- **Updated:** 16 Oct 2026
- **Also known as:** BELL-CVE-2026-74349, DEBIAN-CVE-2026-74349, GHSA-xvwx-4pm6-jf3g, UBUNTU-CVE-2026-74349

## What is CVE-2026-74349?

CVE-2026-74349 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:

ocfs2: reject FITRIM ranges shorter than a cluster

ocfs2_trim_mainbm() trims the global bitmap in cluster units, but its
too-short range validation only checks sb->s_blocksize.

On filesystems with a cluster size larger than the block size, a FITRIM
range that is at least one block but shorter than one cluster is accepted
and shifted down to len == 0.  The later start + len - 1 and len -= ... 
arithmetic then underflows and can drive trimming past the requested
range.

Reject ranges shorter than s_clustersize instead.  That preserves the
existing -EINVAL behavior for requests that cannot discard even one
allocation unit and keeps zero-cluster trims out of the group walk.

## Which versions are affected by CVE-2026-74349?


## How do I fix CVE-2026-74349?

Apply the vendor's patch.

## Is CVE-2026-74349 being exploited?

There is no known exploitation of CVE-2026-74349 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-74349 and fix it if it is affected.

What it is: CVE-2026-74349 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.
Exploitation: There is no known exploitation of CVE-2026-74349 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-2026-74349/ (Markdown: https://insights.sbomify.com/CVE-2026-74349/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-74349
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-74349
- OSV: https://osv.dev/vulnerability/CVE-2026-74349

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-74349/
Summaries are generated and may contain mistakes; the official description above is the record.