# CVE-2026-68442: btrfs: don't propagate EXTENT_FLAG_LOGGING to split extent maps

> A use-after-free vulnerability in the Linux kernel's btrfs filesystem allows attackers to cause a denial of service or potentially execute code.

- **Severity:** High 7.8 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/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:** 12 Aug 2026
- **Updated:** 19 Oct 2026
- **Also known as:** BELL-CVE-2026-68442, DEBIAN-CVE-2026-68442, GHSA-gr86-25pq-rhr2, UBUNTU-CVE-2026-68442

## What is CVE-2026-68442?

CVE-2026-68442 is a high-severity use after free vulnerability in Linux, published on 12 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:

btrfs: don't propagate EXTENT_FLAG_LOGGING to split extent maps

When btrfs_drop_extent_map_range() splits an extent map, the new split
maps inherit the original map's flags through a local 'flags' variable.
Commit f86f7a75e2fb ("btrfs: use the flags of an extent map to identify
the compression type") changed the EXTENT_FLAG_LOGGING clearing to
operate on em->flags instead of that local 'flags' copy, so a split of
an extent map that is currently being logged wrongly inherits
EXTENT_FLAG_LOGGING.

The flag is then never cleared on the split, and when it is freed while
still on the inode's modified_extents list (for example by the extent
map shrinker) it trips the WARN_ON(!list_empty(&em->list)) in
btrfs_free_extent_map() and leads to a use-after-free.

Clear EXTENT_FLAG_LOGGING from the local 'flags' copy used for the
splits and only clear EXTENT_FLAG_PINNED from em->flags, restoring the
behaviour prior to f86f7a75e2fb.

Weakness: CWE-416 (Use After Free)

## Which versions are affected by CVE-2026-68442?


## How do I fix CVE-2026-68442?

Apply the vendor's patch.

## Is CVE-2026-68442 being exploited?

There is no known exploitation of CVE-2026-68442 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-68442 and fix it if it is affected.

What it is: CVE-2026-68442 is a high-severity use after free vulnerability in Linux, published on 12 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-2026-68442 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-2026-68442/ (Markdown: https://insights.sbomify.com/CVE-2026-68442/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-68442
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-68442
- OSV: https://osv.dev/vulnerability/CVE-2026-68442

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-68442/
Summaries are generated and may contain mistakes; the official description above is the record.