# CVE-2026-90256: Bluetooth: L2CAP: use proto_lock for l2cap_data to fix l2cap_disconn_ind

> A race condition in the Linux kernel Bluetooth L2CAP subsystem allows a use-after-free, potentially leading to code execution or privilege escalation.

- **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:** 17 Sep 2026
- **Updated:** 21 Oct 2026
- **Also known as:** AZL-101909, BELL-CVE-2026-90256, DEBIAN-CVE-2026-90256, GHSA-323m-rj3w-9jqp, UBUNTU-CVE-2026-90256

## What is CVE-2026-90256?

CVE-2026-90256 is a high-severity use after free 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: use proto_lock for l2cap_data to fix l2cap_disconn_ind

hci_conn::l2cap_data is accessed without locks in l2cap_disconn_ind via
hci_conn_timeout (disc_work) -> hci_proto_disconn_ind ->
l2cap_disconn_ind.  This is UAF if the l2cap_conn is deleted
concurrently.

disc_work is disabled sync in hci_conn_del(), so we cannot take
hci_dev_lock in disc_work.

Fix by using proto_lock to guard l2cap_data, in addition to hdev->lock
which is held in other access paths.

## Which versions are affected by CVE-2026-90256?


## How do I fix CVE-2026-90256?

Apply the vendor's patch.

## Is CVE-2026-90256 being exploited?

There is no known exploitation of CVE-2026-90256 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-90256 and fix it if it is affected.

What it is: CVE-2026-90256 is a high-severity use after free 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-2026-90256 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-2026-90256/ (Markdown: https://insights.sbomify.com/CVE-2026-90256/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-90256
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-90256
- OSV: https://osv.dev/vulnerability/CVE-2026-90256

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-90256/
Summaries are generated and may contain mistakes; the official description above is the record.