CVE-2026-90004 mm/damon/core: handle region split failure in apply_min_nr_regions()
A null pointer dereference in the Linux kernel DAMON subsystem can cause memory corruption or crashes when region splitting fails due to allocation errors.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Not stated
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-90004?
CVE-2026-90004 is a vulnerability in Linux, published on 16 Sep 2026.
Official description
In the Linux kernel, the following vulnerability has been resolved:
mm/damon/core: handle region split failure in apply_min_nr_regions()
damon_apply_min_nr_regions() repeatedly split each region until its size becomes small enough to meet the user-defined low limit of the number of regions. The loop assumes the split operation (damon_split_region_at()) will always succeed and create the new region. But the operation could silently fail for memory allocation failures, for example.
If such failure happens and the region was the last region, the linked list-based next region fetching returns invalid pointer. As a result, invalid memory dereference and corruption could happen. Even if the corner case is handled, it imposes stress to the allocator by trying split regions for other targets. Fix the issue by breaking all the loops for any region split failure.
This means there could be a min_nr_regions violation. It will only rarely happen since the allocation is arguably too small to fail. Even if it happens, it is only temporal. damon_apply_min_nr_regions() will be called again after the aggregation interval.
The user impact of the issue should be minor, since the allocation is arguably too small to fail. But, it could still theoretically happen, and the consequence is very bad.
This issue was discovered [1] by Sashiko.
Which versions are affected by CVE-2026-90004?
How do I fix CVE-2026-90004?
Apply the vendor's patch.
Is CVE-2026-90004 being exploited?
There is no known exploitation of CVE-2026-90004 in the wild and no public exploit code.
Sources
Also known as DEBIAN-CVE-2026-90004, GHSA-fxh6-hh4r-jg4j, UBUNTU-CVE-2026-90004.