# CVE-2026-90091: Bluetooth: L2CAP: fix race l2cap_sock_cleanup_listen() vs. put_chan

> A race condition in the Linux kernel Bluetooth L2CAP subsystem can lead to a null pointer dereference and system crash.

- **Severity:** High 8.0 (`CVSS:3.1/AV:A/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 17 Sep 2026
- **Updated:** 19 Oct 2026
- **Also known as:** AZL-102777, BELL-CVE-2026-90091, DEBIAN-CVE-2026-90091, GHSA-xgwm-wpg9-2232, UBUNTU-CVE-2026-90091

## What is CVE-2026-90091?

CVE-2026-90091 is a high-severity 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:

Bluetooth: L2CAP: fix race l2cap_sock_cleanup_listen() vs. put_chan

For L2CAP sockets without owning sk->sk_socket, reading
l2cap_pi(sk)->chan may race against concurrent l2cap_sock_kill() ->
l2cap_sock_put_chan().  This excludes simultaneous proto_ops callbacks,
but access in l2cap_sock_cleanup_listen() has unsafe lockless read.

 [Task 1]                         [Task 2 (hdev->workqueue)]
 l2cap_sock_release(parent)       l2cap_disconn_cfm
   l2cap_sock_cleanup_listen        l2cap_conn_del
     bt_accept_dequeue                l2cap_chan_del
       lock_sock(sk)                    l2cap_sock_teardown_cb
       bt_accept_unlink
         bt_sk(sk)->parent = NULL
       release_sock(sk) ----------------> lock_sock(sk)
                                          parent = /* NULL */
     lock_sock(sk) <--------------------- release_sock(sk)
                                          sock_set_flag(sk, SOCK_ZAPPED)
                                      l2cap_sock_close_cb
                                        l2cap_sock_kill(sk)
                                          l2cap_sock_put_chan
     chan = READ l2cap_pi(sk)->chan         l2cap_pi(sk)->chan = NULL
     l2cap_chan_hold_unless_zero            l2cap_put_chan(chan)
       kref_get_unless_zero(&chan->ref)

Task 1 may observe NULL which causes null-ptr-deref.

Fix the race by taking lock_sock() in l2cap_sock_kill() to
synchronize with l2cap_sock_cleanup_listen().  hold_unless_zero() is not
needed here, l2cap_pi(sk)->chan owns reference if it is non-NULL.

Clarify code comments vs. locking.

## Which versions are affected by CVE-2026-90091?


## How do I fix CVE-2026-90091?

Apply the vendor's patch.

## Is CVE-2026-90091 being exploited?

There is no known exploitation of CVE-2026-90091 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-90091 and fix it if it is affected.

What it is: CVE-2026-90091 is a high-severity 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-2026-90091 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-2026-90091/ (Markdown: https://insights.sbomify.com/CVE-2026-90091/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-90091
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-90091
- OSV: https://osv.dev/vulnerability/CVE-2026-90091

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-90091/
Summaries are generated and may contain mistakes; the official description above is the record.