CVE-2026-90005 samples/damon/wsse: handle damon_start() failure
A local attacker with admin privileges can trigger a memory leak and potential use-after-free in the DAMON wsse sample module, leading to denial of service or privilege escalation.
- 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-2026-90005?
CVE-2026-90005 is a 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:
samples/damon/wsse: handle damon_start() failure
Patch series "samples/damon: handle damon_{start,stop}() failures".
All DAMON sample modules are not correctly handling failures from damon_start(). Among those, mtier also has an additional problem for handling of damon_stop() failures. wsse and prcl also have a problem in their damon_call() failure handling. As a result, memory leaks, next DAMON operation disruptions, and use-after-free can happen. Fix those.
Note that only the damon_start() failure caused issues can reliably be reproduced. Reproducing those issues require the admin permission, though.
This patch (of 6):
damon_sample_wsse_start() callers assume it will clean up resources when it fails. And the function does the cleanup for context buildup failures. However, it is not doing the cleanup for damon_start() failure. As a result, when damon_start() fails, it leaks the memory for DAMON context. Free the context in case of the failure to fix the issues.
Note that the issue can reliably be reproduced because the module calls damon_start() in the exclusive mode. For example,
$ sudo damo start $ echo $$ | sudo tee /sys/module/damon_sample_wsse/parameters/target_pid $ echo Y | sudo tee /sys/module/damon_sample_wsse/parameters/enabled $ sudo cat /proc/allocinfo | grep damon_new_ctx
Because the first command is running another DAMON instance, the third command fails the damon_start() call because the new DAMON instance cannot exclusively run. And without this fix, by repeating the third and the fourth commands above, we can show the memory consumption is only increasing due to the leaks. It requires the sudo permission though.
The issue was discovered [1] by Sashiko.
Which versions are affected by CVE-2026-90005?
How do I fix CVE-2026-90005?
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-2026-90005 being exploited?
There is no known exploitation of CVE-2026-90005 in the wild and no public exploit code.
Sources
Also known as BELL-CVE-2026-90005, DEBIAN-CVE-2026-90005, GHSA-rjc9-q3q5-8f95, UBUNTU-CVE-2026-90005.