# CVE-2026-80989: net: thunderbolt: Mark the connection down when bringing it up fails

> A use-after-free in the Linux kernel Thunderbolt network driver allows attackers to cause a denial of service or potentially execute code via crafted connection failures.

- **Severity:** High 8.8 (`CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H`)
- **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:** 11 Sep 2026
- **Updated:** 19 Oct 2026
- **Also known as:** AZL-100764, BELL-CVE-2026-80989, DEBIAN-CVE-2026-80989, GHSA-fm3c-92pm-qq7p, UBUNTU-CVE-2026-80989

## What is CVE-2026-80989?

CVE-2026-80989 is a high-severity use after free vulnerability in Linux, published on 11 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:

net: thunderbolt: Mark the connection down when bringing it up fails

Every failure path in tbnet_connected_work() undoes its own work and
returns without clearing login_sent, so the connection still looks
established. The next tbnet_tear_down() therefore takes its main branch
and repeats a teardown that already happened: it stops rings that are
already stopped, which is a dev_WARN() and fatal under panic_on_warn,
and it releases net->remote_transmit_path even on the HopID mismatch
path, where this connection never owned that id, silently freeing one
that someone else is still using.

Clear login_sent on those paths. That is enough for tbnet_tear_down() to
leave the unwound state alone, and login_received has to stay set: it
records that the peer has logged in and carries the transmit path it gave
us, which nothing on this side can make the peer send again. Two things
change beyond keeping the teardown out of the way: the logout request in
that block is no longer sent, and the peer's next login request now
re-queues our login work rather than connected_work, giving the
connection a fresh login instead of a retry on stale state.

## Which versions are affected by CVE-2026-80989?


## How do I fix CVE-2026-80989?

Apply the vendor's patch.

## Is CVE-2026-80989 being exploited?

There is no known exploitation of CVE-2026-80989 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-80989 and fix it if it is affected.

What it is: CVE-2026-80989 is a high-severity use after free vulnerability in Linux, published on 11 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-2026-80989 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-2026-80989/ (Markdown: https://insights.sbomify.com/CVE-2026-80989/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-80989
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-80989
- OSV: https://osv.dev/vulnerability/CVE-2026-80989

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-80989/
Summaries are generated and may contain mistakes; the official description above is the record.