# CVE-2026-90138: vsock: don't check the listener's sk_err in vsock_accept()

> A logic error in the Linux kernel vsock implementation causes resource leaks and connection rejections, 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:** 17 Sep 2026
- **Updated:** 21 Oct 2026
- **Also known as:** AZL-101975, BELL-CVE-2026-90138, DEBIAN-CVE-2026-90138, GHSA-r47p-87c6-4p5v, UBUNTU-CVE-2026-90138

## What is CVE-2026-90138?

CVE-2026-90138 is a denial of service vulnerability in Linux, published on 17 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:

vsock: don't check the listener's sk_err in vsock_accept()

Syzbot reported an issue which can be reproduced with these steps:
	r0 = socket(AF_VSOCK, SOCK_STREAM, 0)
	bind(r0, {VMADDR_CID_ANY, PORT})
	connect(r0, {VMADDR_CID_LOCAL, PORT}) -> -1, EPROTO (self-connect)
	listen(r0, backlog)                   -> 0
	r1 = socket(AF_VSOCK, SOCK_STREAM, 0)
	connect(r1, {VMADDR_CID_LOCAL, PORT}) -> 0
	accept(r0)                            -> -1, EPROTO (stale sk_err)

Basically, it creates a socket (r0) and triggers a self-connect after
binding it. This self-connect fails with EPROTO because it loops back
to r0 while the socket is still in the TCP_SYN_SENT state, causing it
to be incorrectly dispatched to the connecting-client path. The
unexpected packet type encountered there sets sk_err to EPROTO.

After that, it invokes a listen() call on the same socket. This
listen() call succeeds because the kernel's listening path never
inspects or clears sk_err. Then, a new socket (r1) is created as a
normal client and connects to r0. However, vsock_accept() rejects this
incoming connection because the listener's sk_err still holds the
EPROTO error from the earlier failed self-connect.

This rejection causes the child socket created for r1's connection to
never be freed on virtio or hyperv transports; only the VMCI transport
implements pending_work to revisit and clean up a rejected socket.

For a non-blocking connect(), vsock_connect() may return -EINPROGRESS
immediately, and vsock_connect_timeout() can later set sk->sk_err
asynchronously.

Since no vsock transport ever sets sk_err on a socket while it is in
TCP_LISTEN state, checking it in vsock_accept() serves no purpose and
only carries forward errors left behind by earlier, unrelated
connection attempts on the same socket. Remove the checks so accept()
no longer rejects valid incoming connections because of a stale
error, which also avoids the resource leak described above.

## Which versions are affected by CVE-2026-90138?


## How do I fix CVE-2026-90138?

Apply the vendor's patch.

## Is CVE-2026-90138 being exploited?

There is no known exploitation of CVE-2026-90138 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-90138 and fix it if it is affected.

What it is: CVE-2026-90138 is a denial of service vulnerability in Linux, published on 17 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-2026-90138 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-2026-90138/ (Markdown: https://insights.sbomify.com/CVE-2026-90138/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-90138
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-90138
- OSV: https://osv.dev/vulnerability/CVE-2026-90138

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-90138/
Summaries are generated and may contain mistakes; the official description above is the record.