# CVE-2025-38067: rseq: Fix segfault on registration when rseq_cs is non-zero

> A local attacker can cause a kernel segfault by providing an invalid rseq_cs pointer during registration, 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:** 18 Jun 2025
- **Updated:** 15 Oct 2026
- **Also known as:** AZL-63977, AZL-72710, BELL-CVE-2025-38067, DEBIAN-CVE-2025-38067, GHSA-627j-hqc4-995q, ROOT-OS-DEBIAN-11-CVE-2025-38067, ROOT-OS-DEBIAN-12-CVE-2025-38067, ROOT-OS-UBUNTU-2204-CVE-2025-38067, ROOT-OS-UBUNTU-2404-CVE-2025-38067, UBUNTU-CVE-2025-38067

## What is CVE-2025-38067?

CVE-2025-38067 is a medium-severity vulnerability in Debian Debian Linux, published on 18 Jun 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:

rseq: Fix segfault on registration when rseq_cs is non-zero

The rseq_cs field is documented as being set to 0 by user-space prior to
registration, however this is not currently enforced by the kernel. This
can result in a segfault on return to user-space if the value stored in
the rseq_cs field doesn't point to a valid struct rseq_cs.

The correct solution to this would be to fail the rseq registration when
the rseq_cs field is non-zero. However, some older versions of glibc
will reuse the rseq area of previous threads without clearing the
rseq_cs field and will also terminate the process if the rseq
registration fails in a secondary thread. This wasn't caught in testing
because in this case the leftover rseq_cs does point to a valid struct
rseq_cs.

What we can do is clear the rseq_cs field on registration when it's
non-zero which will prevent segfaults on registration and won't break
the glibc versions that reuse rseq areas on thread creation.

## Which versions are affected by CVE-2025-38067?

It affects 2 products.


Products: Debian Debian Linux, Linux kernel.

## How do I fix CVE-2025-38067?

Apply the vendor's patch.

## Is CVE-2025-38067 being exploited?

There is no known exploitation of CVE-2025-38067 in the wild and no public exploit code.

## Other vulnerabilities in Debian Debian Linux

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- [CVE-2026-24061](https://insights.sbomify.com/CVE-2026-24061/): GNU InetUtils Argument Injection (critical 9.8, exploited in the wild)
- [CVE-2025-39682](https://insights.sbomify.com/CVE-2025-39682/): Linux Kernel Improper Check for Unusual or Exceptional Conditions (critical 9.8, exploited in the wild)
- [CVE-2024-9680](https://insights.sbomify.com/CVE-2024-9680/): Mozilla Firefox Use-After-Free (critical 9.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2025-38067 and fix it if it is affected.

What it is: CVE-2025-38067 is a medium-severity vulnerability in Debian Debian Linux, published on 18 Jun 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-2025-38067 in the wild and no public exploit code.

Affected product: Debian Debian 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-2025-38067/ (Markdown: https://insights.sbomify.com/CVE-2025-38067/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-38067
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-38067
- OSV: https://osv.dev/vulnerability/CVE-2025-38067

---
From sbomify Insights: https://insights.sbomify.com/CVE-2025-38067/
Summaries are generated and may contain mistakes; the official description above is the record.