# CVE-2024-42271: net/iucv: fix use after free in iucv_sock_close()

> A use-after-free vulnerability in the Linux kernel's IUCV socket implementation allows local attackers to cause a system crash via race conditions.

- **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
- **Login needed:** Any signed-in user
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 17 Aug 2024
- **Updated:** 5 Aug 2026
- **Also known as:** AZL-47808, AZL-47853, BELL-CVE-2024-42271, DEBIAN-CVE-2024-42271, GHSA-gqp6-8ccj-768w, ROOT-OS-DEBIAN-11-CVE-2024-42271, UBUNTU-CVE-2024-42271

## What is CVE-2024-42271?

CVE-2024-42271 is a high-severity use after free vulnerability in Linux kernel, published on 17 Aug 2024. 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/iucv: fix use after free in iucv_sock_close()

iucv_sever_path() is called from process context and from bh context.
iucv->path is used as indicator whether somebody else is taking care of
severing the path (or it is already removed / never existed).
This needs to be done with atomic compare and swap, otherwise there is a
small window where iucv_sock_close() will try to work with a path that has
already been severed and freed by iucv_callback_connrej() called by
iucv_tasklet_fn().

Example:
[452744.123844] Call Trace:
[452744.123845] ([<0000001e87f03880>] 0x1e87f03880)
[452744.123966]  [<00000000d593001e>] iucv_path_sever+0x96/0x138
[452744.124330]  [<000003ff801ddbca>] iucv_sever_path+0xc2/0xd0 [af_iucv]
[452744.124336]  [<000003ff801e01b6>] iucv_sock_close+0xa6/0x310 [af_iucv]
[452744.124341]  [<000003ff801e08cc>] iucv_sock_release+0x3c/0xd0 [af_iucv]
[452744.124345]  [<00000000d574794e>] __sock_release+0x5e/0xe8
[452744.124815]  [<00000000d5747a0c>] sock_close+0x34/0x48
[452744.124820]  [<00000000d5421642>] __fput+0xba/0x268
[452744.124826]  [<00000000d51b382c>] task_work_run+0xbc/0xf0
[452744.124832]  [<00000000d5145710>] do_notify_resume+0x88/0x90
[452744.124841]  [<00000000d5978096>] system_call+0xe2/0x2c8
[452744.125319] Last Breaking-Event-Address:
[452744.125321]  [<00000000d5930018>] iucv_path_sever+0x90/0x138
[452744.125324]
[452744.125325] Kernel panic - not syncing: Fatal exception in interrupt

Note that bh_lock_sock() is not serializing the tasklet context against
process context, because the check for sock_owned_by_user() and
corresponding handling is missing.

Ideas for a future clean-up patch:
A) Correct usage of bh_lock_sock() in tasklet context, as described in
Re-enqueue, if needed. This may require adding return values to the
tasklet functions and thus changes to all users of iucv.

B) Change iucv tasklet into worker and use only lock_sock() in af_iucv.

Weakness: CWE-416 (Use After Free)

## Which versions are affected by CVE-2024-42271?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2024-42271?

Apply the vendor's patch.

## Is CVE-2024-42271 being exploited?

There is no known exploitation of CVE-2024-42271 in the wild and no public exploit code.

## Other vulnerabilities in Linux kernel

- [CVE-2026-53266](https://insights.sbomify.com/CVE-2026-53266/): Linux Kernel Out-of-Bounds Write (high 8.8, exploited in the wild)
- [CVE-2013-6282](https://insights.sbomify.com/CVE-2013-6282/): Linux Kernel Improper Input Validation (high 8.8, exploited in the wild)
- [CVE-2022-0185](https://insights.sbomify.com/CVE-2022-0185/): Linux Kernel Heap-Based Buffer Overflow (high 8.4, exploited in the wild)
- [CVE-2013-2094](https://insights.sbomify.com/CVE-2013-2094/): Linux Kernel Privilege Escalation (high 8.4, exploited in the wild)
- [CVE-2026-53362](https://insights.sbomify.com/CVE-2026-53362/): Linux Kernel Unspecified (high 7.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2024-42271 and fix it if it is affected.

What it is: CVE-2024-42271 is a high-severity use after free vulnerability in Linux kernel, published on 17 Aug 2024. 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-2024-42271 in the wild and no public exploit code.

Affected product: Linux kernel. 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-2024-42271/ (Markdown: https://insights.sbomify.com/CVE-2024-42271/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2024-42271
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2024-42271
- OSV: https://osv.dev/vulnerability/CVE-2024-42271

---
From sbomify Insights: https://insights.sbomify.com/CVE-2024-42271/
Summaries are generated and may contain mistakes; the official description above is the record.