CVE-2026-89965 nvdimm/btt: reject an arena whose nfree is below the lane count
An out-of-bounds write in the Linux kernel NVDIMM BTT driver allows attackers to cause memory corruption and potential code execution via a crafted arena.
- 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
What is CVE-2026-89965?
CVE-2026-89965 is a high-severity memory corruption vulnerability in Linux, published on 16 Sep 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:
nvdimm/btt: reject an arena whose nfree is below the lane count
The BTT info block's nfree field, the number of reserve free blocks, is read from the medium without validation. btt_freelist_init() and btt_rtt_init() size the per-lane freelist[] and rtt[] arrays by nfree, but the I/O path indexes them by the lane from nd_region_acquire_lane(), which is bounded by nd_region->num_lanes (ND_MAX_LANES), not by nfree. A crafted or foreign arena whose nfree is below the lane count makes freelist[lane]/rtt[lane] run past the allocation: an out-of-bounds write.
btt.rst documents the nlanes = min(nfree, num_cpus) invariant, which the code does not currently honor: num_lanes is ND_MAX_LANES regardless of nfree. Reject an arena whose nfree is below num_lanes at discovery, before the per-lane arrays are allocated, enforcing that invariant.
Which versions are affected by CVE-2026-89965?
How do I fix CVE-2026-89965?
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-2026-89965 being exploited?
There is no known exploitation of CVE-2026-89965 in the wild and no public exploit code.
Sources
Also known as AZL-101126, BELL-CVE-2026-89965, DEBIAN-CVE-2026-89965, GHSA-gj9w-7mfp-hc5m, UBUNTU-CVE-2026-89965.