# 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.

- **Severity:** Not scored
- **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:** Yes
- **Published:** 24 Sep 2026
- **Updated:** 3 Oct 2026
- **Also known as:** AZL-103844, BELL-CVE-2026-93795, DEBIAN-CVE-2026-93795, GHSA-q3xm-frv6-mwqx, UBUNTU-CVE-2026-93795

## 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.

## Is CVE-2026-93795 being exploited?

There is no known exploitation of CVE-2026-93795 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-93795 and fix it if it is affected.

What it is: 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.
Exploitation: There is no known exploitation of CVE-2026-93795 in the wild and no public exploit code.

Affected product: Linux. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-93795/ (Markdown: https://insights.sbomify.com/CVE-2026-93795/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-93795
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-93795
- OSV: https://osv.dev/vulnerability/CVE-2026-93795

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-93795/
Summaries are generated and may contain mistakes; the official description above is the record.