# CVE-2026-80631: btrfs: lzo: reject compressed segment that overflows the compressed input

> A crafted Btrfs filesystem image can cause a kernel null pointer dereference and crash during LZO decompression, leading to denial of service.

- **Severity:** High 7.5 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 28 Aug 2026
- **Updated:** 21 Oct 2026
- **Also known as:** AZL-98102, BELL-CVE-2026-80631, DEBIAN-CVE-2026-80631, GHSA-hqpg-7vj3-59jv, UBUNTU-CVE-2026-80631

## What is CVE-2026-80631?

CVE-2026-80631 is a high-severity vulnerability in Linux, published on 28 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

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

btrfs: lzo: reject compressed segment that overflows the compressed input

lzo_decompress_bio() validates each on-disk segment length seg_len only
against the workspace cbuf size, not against the compressed input size
(compressed_len, the total folio bytes of the bio).  A crafted extent can
carry a segment whose seg_len passes the cbuf check but runs past the end
of the bio, so copy_compressed_segment() walks off the last folio:
get_current_folio() then returns the NULL folio from bio_next_folio(), and
with CONFIG_BTRFS_ASSERT disabled (default) folio_size(NULL) faults.

 BUG: KASAN: null-ptr-deref in lzo_decompress_bio (fs/btrfs/lzo.c:383)
 Read of size 8 at addr 0000000000000000 by task kworker/u8:1/29
 Workqueue: btrfs-endio simple_end_io_work
  kasan_report (mm/kasan/report.c:590)
  lzo_decompress_bio (fs/btrfs/lzo.c:383)
  end_bbio_compressed_read (fs/btrfs/compression.c:1065)
  btrfs_bio_end_io (fs/btrfs/bio.c:135)
  btrfs_check_read_bio (fs/btrfs/bio.c:180 fs/btrfs/bio.c:285)
  simple_end_io_work
  process_one_work
  worker_thread

Reject any segment whose payload would extend beyond compressed_len before
copying it, treating it as corruption like the other on-disk validation
failures in this function.

## Which versions are affected by CVE-2026-80631?


## How do I fix CVE-2026-80631?

Apply the vendor's patch.

## Is CVE-2026-80631 being exploited?

There is no known exploitation of CVE-2026-80631 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-80631 and fix it if it is affected.

What it is: CVE-2026-80631 is a high-severity vulnerability in Linux, published on 28 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-80631 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-2026-80631/ (Markdown: https://insights.sbomify.com/CVE-2026-80631/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-80631
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-80631
- OSV: https://osv.dev/vulnerability/CVE-2026-80631

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-80631/
Summaries are generated and may contain mistakes; the official description above is the record.