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.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
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.
Upgrade to the fixed version. Memory-safe languages, compiler hardening and fuzzing prevent most new cases. More about Memory corruption.
Is CVE-2026-89494 being exploited?
There is no known exploitation of CVE-2026-89494 in the wild and no public exploit code.
Sources
Also known as AZL-100680, BELL-CVE-2026-89494, DEBIAN-CVE-2026-89494, GHSA-hhc4-rpwx-gp2p, UBUNTU-CVE-2026-89494.