# CVE-2025-38544: rxrpc: Fix bug due to prealloc collision

> A bug in the Linux kernel's rxrpc module causes assertion failures during error handling, potentially leading to a denial of service.

- **Severity:** Medium 5.5 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/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:** 16 Aug 2025
- **Updated:** 11 May 2026
- **Also known as:** AZL-66380, AZL-70457, BELL-CVE-2025-38544, DEBIAN-CVE-2025-38544, GHSA-2fgf-j87m-qgrf, ROOT-OS-DEBIAN-11-CVE-2025-38544, ROOT-OS-DEBIAN-12-CVE-2025-38544, ROOT-OS-UBUNTU-2204-CVE-2025-38544, ROOT-OS-UBUNTU-2404-CVE-2025-38544, UBUNTU-CVE-2025-38544

## What is CVE-2025-38544?

CVE-2025-38544 is a medium-severity vulnerability in Linux kernel, published on 16 Aug 2025. 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:

rxrpc: Fix bug due to prealloc collision

When userspace is using AF_RXRPC to provide a server, it has to preallocate
incoming calls and assign to them call IDs that will be used to thread
related recvmsg() and sendmsg() together.  The preallocated call IDs will
automatically be attached to calls as they come in until the pool is empty.

To the kernel, the call IDs are just arbitrary numbers, but userspace can
use the call ID to hold a pointer to prepared structs.  In any case, the
user isn't permitted to create two calls with the same call ID (call IDs
become available again when the call ends) and EBADSLT should result from
sendmsg() if an attempt is made to preallocate a call with an in-use call
ID.

However, the cleanup in the error handling will trigger both assertions in
rxrpc_cleanup_call() because the call isn't marked complete and isn't
marked as having been released.

Fix this by setting the call state in rxrpc_service_prealloc_one() and then
marking it as being released before calling the cleanup function.

Weakness: CWE-617 (Reachable Assertion)

## Which versions are affected by CVE-2025-38544?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2025-38544?

Apply the vendor's patch.

## Is CVE-2025-38544 being exploited?

There is no known exploitation of CVE-2025-38544 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-2025-38544 and fix it if it is affected.

What it is: CVE-2025-38544 is a medium-severity vulnerability in Linux kernel, published on 16 Aug 2025. 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-2025-38544 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-2025-38544/ (Markdown: https://insights.sbomify.com/CVE-2025-38544/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-38544
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-38544
- OSV: https://osv.dev/vulnerability/CVE-2025-38544

---
From sbomify Insights: https://insights.sbomify.com/CVE-2025-38544/
Summaries are generated and may contain mistakes; the official description above is the record.