# CVE-2026-98289: af_unix: Unify scc_index when finalising SCC in __unix_walk_scc().

> A logic error in the Linux kernel's Unix socket garbage collector can cause memory leaks, leading to denial of service.

- **Severity:** Not scored
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 6 Oct 2026
- **Updated:** 19 Oct 2026
- **Also known as:** AZL-106236, BELL-CVE-2026-98289, DEBIAN-CVE-2026-98289, GHSA-3rq9-mjhw-q3g6, UBUNTU-CVE-2026-98289

## What is CVE-2026-98289?

CVE-2026-98289 is a memory corruption vulnerability in Linux, published on 6 Oct 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: Unify scc_index when finalising SCC in __unix_walk_scc().

Commit bfdb01283ee8 ("af_unix: Assign a unique index to SCC.")
changed Tarjan's algorithm to update lowlink with lowlink,
which is called lowpoint (unix_vertex.scc_index).

unix_vertex_dead() assumes all vertices in an SCC share the same
lowpoint, but this is not always true if an SCC has two or more
back edges, depending on the order of DFS.

For example, the graph below has two back edges from B to A
and from C to B.

  A --> B --> C
  ^    | ^    |
  `----' `----'

If DFS walks through A -> B -> C -> B (-> C -> B) -> A (-> B -> A),
each index and scc_index will be updated as follows.

  A --> B --> C    C = (3, 3)  (index, scc_index)
                   B = (2, 2)
                   A = (1, 1)

  A ... B ... C    C = (3, 2)<-.
         ^    |    B = (2, 2) -'
         `----'    A = (1, 1)

  A ... B ... C    C = (3, 2)
  ^    | .    .    B = (2, 1)<-.
  `----'  ....     A = (1, 1) -'

Then, unix_vertex_dead() thinks that B is passed to another
SCC with scc_index 2, and the SCC is not garbage-collected.

This does not happen if DFS walks in a different order below
or starts from B.

    1      3
  A --> B --> C
  ^    | ^    |
  `----' `----'
     2      4

Let's unify scc_index across the SCC when finalising it.

Note that updating v->index was previously done in unix_scc_dead(),
when called from __unix_walk_scc(), just to save one loop.  Since
__unix_walk_scc() now iterates over the SCC anyway, the update is
moved back to __unix_walk_scc() and 'fast' argument is dropped.

## Which versions are affected by CVE-2026-98289?


## How do I fix CVE-2026-98289?

Apply the vendor's patch.

## Is CVE-2026-98289 being exploited?

There is no known exploitation of CVE-2026-98289 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-98289 and fix it if it is affected.

What it is: CVE-2026-98289 is a memory corruption vulnerability in Linux, published on 6 Oct 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-2026-98289 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-2026-98289/ (Markdown: https://insights.sbomify.com/CVE-2026-98289/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-98289
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-98289
- OSV: https://osv.dev/vulnerability/CVE-2026-98289

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-98289/
Summaries are generated and may contain mistakes; the official description above is the record.