# CVE-2026-74535: Bluetooth: ISO: avoid deadlocks in iso_sock_timeout

> A use-after-free vulnerability in the Linux kernel's Bluetooth ISO subsystem allows attackers to cause a denial of service or potentially execute code via concurrent operations.

- **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:** 15 Aug 2026
- **Updated:** 16 Oct 2026
- **Also known as:** BELL-CVE-2026-74535, DEBIAN-CVE-2026-74535, GHSA-m6r7-j582-3j5f, UBUNTU-CVE-2026-74535

## What is CVE-2026-74535?

CVE-2026-74535 is a high-severity use after free vulnerability in Linux, published on 15 Aug 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: ISO: avoid deadlocks in iso_sock_timeout

iso_sock_timeout() takes lock_sock, so sync disabling the timer while
holding that lock may deadlock.

iso_sock_timeout() may also run concurrently with iso_conn_del(), which
leads to UAF

        [Task 1]                      [Task hdev->workqueue]
        iso_sock_timeout              iso_conn_del
          iso_conn_hold_unless_zero     iso_chan_del
                           `------------> iso_conn_put
                                      caller frees hcon
          iso_conn_put
            iso_conn_free
              conn->hcon->iso_data = NULL; /* UAF */

Fix the deadlock by removing the disable from the lock_sock sections.
Move the timer from iso_conn to iso_pinfo to decouple it from iso_conn
which may need to be freed in lock_sock section. Convert some of the
clear_timer to disable_timer.

## Which versions are affected by CVE-2026-74535?


## How do I fix CVE-2026-74535?

Apply the vendor's patch.

## Is CVE-2026-74535 being exploited?

There is no known exploitation of CVE-2026-74535 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-74535 and fix it if it is affected.

What it is: CVE-2026-74535 is a high-severity use after free vulnerability in Linux, published on 15 Aug 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-2026-74535 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-2026-74535/ (Markdown: https://insights.sbomify.com/CVE-2026-74535/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-74535
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-74535
- OSV: https://osv.dev/vulnerability/CVE-2026-74535

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-74535/
Summaries are generated and may contain mistakes; the official description above is the record.