# CVE-2026-80521: af_unix: Unlink scc_entry in unix_del_edge().

> A race condition in Linux kernel Unix socket garbage collection can lead to use-after-free, potentially allowing local attackers to execute code or escalate privileges.

- **Severity:** High 7.8 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H`)
- **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:** 26 Aug 2026
- **Updated:** 3 Oct 2026
- **Also known as:** AZL-97814, BELL-CVE-2026-80521, DEBIAN-CVE-2026-80521, GHSA-g8mr-r59r-2xmq, UBUNTU-CVE-2026-80521

## What is CVE-2026-80521?

CVE-2026-80521 is a high-severity use after free vulnerability in Linux, published on 26 Aug 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:

af_unix: Unlink scc_entry in unix_del_edge().

Kyle Zeng reported that GC could free a dead SCC partially.

The scenario is as follows:

   1) Create two SCCs:

       X -.   A <-> B
       ^--'

   2) Run the following concurrently:

      2-1) send() sk-B to sk-B from sk-X
      2-2) close() both A and B

At 2-1), there is a small window where unix_add_edges()
publishes a new edge (B <-> B) to GC but its skb is not queued
by skb_queue_tail().

If 2-2) completes before skb_queue_tail() and GC is triggered,
it judges A <-> B as dead, but B is not freed because GC cannot
collect the not-yet-queued skb holding the B <-> B edge.

       X -.   A <-> B -. This edge is visible
       ^--'         ^..'  but skb is not

This itself is not a problem since the next GC run will judge
B as dead as well and free it finally.

       X -.   A <.> B -.
       ^--'         ^--'

However, X's SCC forces the next GC to call unix_walk_scc_fast(),
and it iterates over A through B's scc_entry.

Let's unlink scc_entry before freeing the vertex in unix_del_edge().

## Which versions are affected by CVE-2026-80521?


## How do I fix CVE-2026-80521?

Apply the vendor's patch.

## Is CVE-2026-80521 being exploited?

There is no known exploitation of CVE-2026-80521 in the wild and no public exploit code.

Public exploit code:

- container escape POCs for CVE-2026-80521 and CVE-2026-52910 (github_poc): https://github.com/Markakd/Container_escape
- container escape POCs for CVE-2026-80521 and CVE-2026-52910 (github_poc): https://github.com/rifkyards/Container_escape-CVE-2026-80521-CVE-2026-52910

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-80521 and fix it if it is affected.

What it is: CVE-2026-80521 is a high-severity use after free vulnerability in Linux, published on 26 Aug 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-2026-80521 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-2026-80521/ (Markdown: https://insights.sbomify.com/CVE-2026-80521/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-80521
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-80521
- OSV: https://osv.dev/vulnerability/CVE-2026-80521

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-80521/
Summaries are generated and may contain mistakes; the official description above is the record.