CVE-2026-31458 mm/damon/sysfs: check contexts->nr before accessing contexts_arr[0]
Privileged users can trigger a NULL pointer dereference in the Linux kernel DAMON subsystem by setting context count to zero, causing a denial of service.
- 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-2026-31458?
CVE-2026-31458 is a medium-severity vulnerability in Linux kernel, published on 22 Apr 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:
mm/damon/sysfs: check contexts->nr before accessing contexts_arr[0]
Multiple sysfs command paths dereference contexts_arr[0] without first verifying that kdamond->contexts->nr == 1. A user can set nr_contexts to 0 via sysfs while DAMON is running, causing NULL pointer dereferences.
In more detail, the issue can be triggered by privileged users like below.
First, start DAMON and make contexts directory empty (kdamond->contexts->nr == 0).
# damo start # cd /sys/kernel/mm/damon/admin/kdamonds/0 # echo 0 > contexts/nr_contexts
Then, each of below commands will cause the NULL pointer dereference.
# echo update_schemes_stats > state # echo update_schemes_tried_regions > state # echo update_schemes_tried_bytes > state # echo update_schemes_effective_quotas > state # echo update_tuned_intervals > state
Guard all commands (except OFF) at the entry point of damon_sysfs_handle_cmd().
Weakness: CWE-476
Which versions are affected by CVE-2026-31458?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2026-31458?
Apply the vendor's patch.
Is CVE-2026-31458 being exploited?
There is no known exploitation of CVE-2026-31458 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as AZL-83228, BELL-CVE-2026-31458, DEBIAN-CVE-2026-31458, GHSA-rhx5-38hr-wvr9, ROOT-OS-DEBIAN-12-CVE-2026-31458, ROOT-OS-DEBIAN-13-CVE-2026-31458 and 2 more.