CVE-2026-89570 cxl/mce: Make the MCE notifier per-region
A use-after-free vulnerability in the Linux kernel CXL MCE notifier can cause NULL dereferences and system crashes.
- 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-2026-89570?
CVE-2026-89570 is a high-severity use after free vulnerability in Linux, published on 11 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:
cxl/mce: Make the MCE notifier per-region
Flavien Solt reported lifetime issues with the CXL MCE notifier, which can lead to NULL dereferences and use-after-free in the MCE handler. The notifier was registered per memory device and stored in 'struct cxl_memdev_state', even though it only needs the region state (the region's SPA range and its extended linear cache size).
Instead of keeping the memory device and endpoint alive, the correct fix is to move the notifier into 'struct cxl_region' and register it from cxl_region_probe() as it should be a per-region notifier. Setup the registration to only happen for regions that have an extended linear cache as that is the only current usage.
Remove cxl_port_get_spa_cache_alias() as it is now dead code.
[ dj: Update dev_warn() when notifier fails due to kconfig. (Ben) ]
Which versions are affected by CVE-2026-89570?
How do I fix CVE-2026-89570?
Apply the vendor's patch.
Upgrade to the fixed version. These bugs are found with fuzzing and sanitisers and avoided by memory-safe languages. More about Use after free.
Is CVE-2026-89570 being exploited?
There is no known exploitation of CVE-2026-89570 in the wild and no public exploit code.
Sources
Also known as BELL-CVE-2026-89570, DEBIAN-CVE-2026-89570, GHSA-5c9g-7vf9-4pwc, UBUNTU-CVE-2026-89570.