CVE-2026-64458 mm/damon/ops-common: handle extreme intervals in damon_hot_score()
A local attacker with sysfs write permissions can cause a kernel crash via divide-by-zero or out-of-bounds access in DAMON monitoring.
- Exploited in the wild
- Not known
- Login needed
- An administrator
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-64458?
CVE-2026-64458 is a vulnerability in Linux, published on 25 Jul 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/ops-common: handle extreme intervals in damon_hot_score()
Fix three issues in damon_hot_score() that comes from wrong handling of extreme (zero or too high) monitoring intervals user setup.
When the user sets sampling interval zero, damon_max_nr_accesses(), which is called from damon_hot_score(), causes a divide-by-zero. Needless to say, it is a problem.
When the user sets the aggregation interval zero, the function returns zero. It is wrong, since the real maximum nr_acceses in the setup should be one. Worse yet, it can cause another divide-by-zero from its caller, damon_hot_score(), since it uses damon_max_nr_accesses() return value as a denominator.
When the user sets the aggregation interval very high, damon_hot_score() could return a value out of [0, DAMOS_MAX_SCORE] range. Since the return value is used as an index to the regions_score_histogram array, which is DAMOS_MAX_SCORE+1 size, it causes out of bounds array access.
The issues can be relatively easily reproduced like below. The sysfs write permission is required, though.
# ./damo start --damos_action lru_prio --damos_quota_space 100M \ --damos_quota_interval 1s # cd /sys/kernel/mm/damon/admin/kdamonds/0 # echo 0 > contexts/0/monitoring_attrs/intervals/sample_us # echo 0 > contexts/0/monitoring_attrs/intervals/aggr_us # echo commit > state # dmesg [...] [ 131.329762] Oops: divide error: 0000 [#1] SMP NOPTI [...] [ 131.336089] RIP: 0010:damon_hot_score+0x27/0xd0 [...]
Fix the divide-by-zero intervals problems by explicitly handling the zero intervals in damon_max_nr_accesses(). Fix the out-of-bound array access by applying [0, DAMOS_MAX_SCORE] bounds before returning from damon_hot_score().
The issue was discovered [1] by Sashiko.
Which versions are affected by CVE-2026-64458?
How do I fix CVE-2026-64458?
Apply the vendor's patch.
Is CVE-2026-64458 being exploited?
There is no known exploitation of CVE-2026-64458 in the wild and no public exploit code.
Sources
Also known as BELL-CVE-2026-64458, DEBIAN-CVE-2026-64458, GHSA-fhqc-6xwp-7x74, ROOT-OS-UBUNTU-2204-CVE-2026-64458, UBUNTU-CVE-2026-64458.