# CVE-2026-89494: ocfs2: validate lengths in dlm_mig_lockres_handler

> A remote attacker can trigger out-of-bounds reads and writes in the Linux kernel OCFS2 DLM handler, causing a system crash or potential code execution.

- **Severity:** Critical 9.8 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/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:** 11 Sep 2026
- **Updated:** 19 Oct 2026
- **Also known as:** AZL-100680, BELL-CVE-2026-89494, DEBIAN-CVE-2026-89494, GHSA-hhc4-rpwx-gp2p, UBUNTU-CVE-2026-89494

## What is CVE-2026-89494?

CVE-2026-89494 is a critical memory corruption vulnerability in Linux, published on 11 Sep 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:

ocfs2: validate lengths in dlm_mig_lockres_handler

A node receiving a DLM_MIG_LOCKRES message trusts several fields of the
peer-supplied dlm_migratable_lockres without validation.  num_locks and
lockname_len are bounded only on the sending side, and the message is
never checked to actually carry num_locks migratable_lock entries.  As a
result dlm_process_recovery_data() walks mres->ml[0..num_locks) past the
kmalloc(data_len) copy of the message (an out-of-bounds read that ends in
a BUG_ON panic), and dlm_init_lockres() copies lockname_len bytes into the
fixed 32-byte o2dlm_lockname slab object (a heap out-of-bounds write). 
Both are reachable by any node in the domain.

Validate these fields right after dlm_grab(), before anything uses them --
including the not-joined error path, which already prints mres->lockname
with the unbounded lockname_len as a %.*s precision.  Reject the message
unless lockname_len <= DLM_LOCKID_NAME_MAX, num_locks <=
DLM_MAX_MIGRATABLE_LOCKS (the bound the sender already asserts), and the
payload is large enough to hold the claimed locks.  Conforming recovery
and migration messages are unaffected.

## Which versions are affected by CVE-2026-89494?


## How do I fix CVE-2026-89494?

Apply the vendor's patch.

## Is CVE-2026-89494 being exploited?

There is no known exploitation of CVE-2026-89494 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-89494 and fix it if it is affected.

What it is: CVE-2026-89494 is a critical memory corruption vulnerability in Linux, published on 11 Sep 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-2026-89494 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-2026-89494/ (Markdown: https://insights.sbomify.com/CVE-2026-89494/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-89494
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-89494
- OSV: https://osv.dev/vulnerability/CVE-2026-89494

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-89494/
Summaries are generated and may contain mistakes; the official description above is the record.