# CVE-2026-99054: tipc: destroy topsrv workqueues before closing connections


- **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
- **Fix available:** Yes
- **Published:** 23 Oct 2026
- **Updated:** 24 Oct 2026
- **Also known as:** AZL-110936, BELL-CVE-2026-99054, DEBIAN-CVE-2026-99054, GHSA-qw7p-7wvc-p5q5, UBUNTU-CVE-2026-99054

## What is CVE-2026-99054?

CVE-2026-99054 is a high-severity vulnerability in Linux, published on 23 Oct 2026. 

### Official description

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

tipc: destroy topsrv workqueues before closing connections

tipc_topsrv_stop() closed subscriber connections while the topology
server's send and receive workqueues were still running. Socket
callbacks and subscription events could then queue more work, and
in-flight send/recv work could drop the last connection reference
during the conn_idr walk.

That race produced several teardown failures: refcount_t addition on
0 from conn_get() on a connection whose release was blocked on
idr_lock, a subsequent use-after-free in tipc_conn_close(),
queue_work() on an already destroyed workqueue from the listener
data-ready callback, and an RCU stall in tipc_topsrv_exit_net()
while the walk spun under idr_lock.

Clear srv->listener under idr_lock so it acts as a shutdown flag,
skip queue_work() once it is NULL, destroy the workqueues to flush
in-flight work, and only then close the remaining connections.
Refuse tipc_conn_lookup() after that flag is cleared, and drop
idr_lock when the teardown walk finds no connection, so an
in-flight subscription event cannot pin idr_in_use while the
walk holds the lock.

v3 supersedes the narrower in-thread diff Tung Quang Nguyen
posted on 2026-09-23. It keeps his teardown order and adds the
lookup refusal and the empty-idr unlock.

## Which versions are affected by CVE-2026-99054?


## How do I fix CVE-2026-99054?

Upgrade to a fixed version.

## Is CVE-2026-99054 being exploited?

There is no known exploitation of CVE-2026-99054 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-99054 and fix it if it is affected.

What it is: CVE-2026-99054 is a high-severity vulnerability in Linux, published on 23 Oct 2026. 
Exploitation: There is no known exploitation of CVE-2026-99054 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-2026-99054/ (Markdown: https://insights.sbomify.com/CVE-2026-99054/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-99054
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-99054
- OSV: https://osv.dev/vulnerability/CVE-2026-99054

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-99054/
Summaries are generated and may contain mistakes; the official description above is the record.