# CVE-2026-99213: vsock: treat TCP_CLOSING as once-established


- **Severity:** Not scored
- **Exploited in the wild:** Not known
- **Fix available:** Yes
- **Published:** 28 Oct 2026
- **Updated:** 28 Oct 2026
- **Also known as:** AZL-111380, BELL-CVE-2026-99213, DEBIAN-CVE-2026-99213, GHSA-5hph-w22r-x9jx, UBUNTU-CVE-2026-99213

## What is CVE-2026-99213?

CVE-2026-99213 is a vulnerability in Linux, published on 28 Oct 2026. 

### Official description

In the Linux kernel, the following vulnerability has been resolved:

vsock: treat TCP_CLOSING as once-established

Handle the TCP_ESTABLISHED -> TCP_CLOSING transition on OP_RST, which can
race with the connect loop. Immediately break and return 0 on
ESTABLISHED/CLOSING. The return value of connect() should reflect what
happened up to the point the connection was established or failed. Events
that occur afterwards must not affect it. E.g. even if OP_RW has already
set sk_err, connect() should still return 0, not ENOBUFS because of it.
Adapt the inaccurate comment above signal_pending().

Resetting a socket that is still present in connected_table can lead to
memory corruption. The reporter noted lost transports for in-flight skbs,
and I have reproduced crashes caused by re-insertion into connected_table.

  list_add double add: new=, prev=, next=.
  kernel BUG at lib/list_debug.c:35!
  Oops: invalid opcode: 0000 [#1] SMP KASAN NOPTI
  Workqueue: vsock-loopback vsock_loopback_work
  RIP: 0010:__list_add_valid_or_report+0x11f/0x130
  Call Trace:
   vsock_insert_connected.cold+0xe/0x13
   virtio_transport_recv_pkt+0x10e9/0x1460
   vsock_loopback_work+0x305/0x480
   process_one_work+0xe4c/0x1560
   worker_thread+0x4f1/0xd60
   kthread+0x36e/0x470
   ret_from_fork+0x47b/0x6b0
   ret_from_fork_asm+0x1a/0x30

This fix is supplementary to commit 002541ef650b ("vsock: Ignore
signal/timeout on connect() if already established"). Details under Link.

## Which versions are affected by CVE-2026-99213?


## How do I fix CVE-2026-99213?

Upgrade to a fixed version.

## Is CVE-2026-99213 being exploited?

There is no known exploitation of CVE-2026-99213 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-99213 and fix it if it is affected.

What it is: CVE-2026-99213 is a vulnerability in Linux, published on 28 Oct 2026. 
Exploitation: There is no known exploitation of CVE-2026-99213 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-2026-99213/ (Markdown: https://insights.sbomify.com/CVE-2026-99213/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-99213
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-99213
- OSV: https://osv.dev/vulnerability/CVE-2026-99213

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-99213/
Summaries are generated and may contain mistakes; the official description above is the record.