CVE-2026-93795 blk-cgroup: fix leaks and online flag on radix_tree_insert failure
A local attacker can trigger a memory leak in the Linux kernel's block cgroup subsystem, leading to resource exhaustion and 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-2026-93795?
CVE-2026-93795 is a memory corruption vulnerability in Linux, published on 24 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:
blk-cgroup: fix leaks and online flag on radix_tree_insert failure
When radix_tree_insert() fails in blkg_create(), the error path has two issues:
1. blkg->online is set to true unconditionally, even when the blkg was never fully inserted. Move the assignment inside the success block.
2. The error path calls blkg_put() without first calling percpu_ref_kill(). Because the refcount is still in percpu mode, percpu_ref_put() only does this_cpu_sub() without checking for zero, so blkg_release() is never triggered. This permanently leaks the blkg memory, its percpu iostat, policy data, the parent blkg reference, and the cgroup css reference — the latter preventing the cgroup from ever being destroyed.
Fix by replacing blkg_put() with percpu_ref_kill(), matching the pattern used in blkg_destroy().
Which versions are affected by CVE-2026-93795?
How do I fix CVE-2026-93795?
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-2026-93795 being exploited?
There is no known exploitation of CVE-2026-93795 in the wild and no public exploit code.
Sources
Also known as AZL-103844, BELL-CVE-2026-93795, DEBIAN-CVE-2026-93795, GHSA-q3xm-frv6-mwqx, UBUNTU-CVE-2026-93795.