# CVE-2025-40063: crypto: comp - Use same definition of context alloc and free ops

> A Linux kernel memory corruption vulnerability in the crypto subsystem allows attackers to potentially execute arbitrary code or escalate privileges due to struct layout mismatches.

- **Severity:** High 7.0 (`CVSS:3.1/AV:L/AC:H/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:** 28 Oct 2025
- **Updated:** 5 Aug 2026
- **Also known as:** BELL-CVE-2025-40063, DEBIAN-CVE-2025-40063, GHSA-94hr-47ff-rmcx, UBUNTU-CVE-2025-40063

## What is CVE-2025-40063?

CVE-2025-40063 is a high-severity memory corruption vulnerability in Linux, published on 28 Oct 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:

crypto: comp - Use same definition of context alloc and free ops

In commit 42d9f6c77479 ("crypto: acomp - Move scomp stream allocation
code into acomp"), the crypto_acomp_streams struct was made to rely on
having the alloc_ctx and free_ctx operations defined in the same order
as the scomp_alg struct. But in that same commit, the alloc_ctx and
free_ctx members of scomp_alg may be randomized by structure layout
randomization, since they are contained in a pure ops structure
(containing only function pointers). If the pointers within scomp_alg
are randomized, but those in crypto_acomp_streams are not, then
the order may no longer match. This fixes the problem by removing the
union from scomp_alg so that both crypto_acomp_streams and scomp_alg
will share the same definition of alloc_ctx and free_ctx, ensuring
they will always have the same layout.

## Which versions are affected by CVE-2025-40063?


## How do I fix CVE-2025-40063?

Apply the vendor's patch.

## Is CVE-2025-40063 being exploited?

There is no known exploitation of CVE-2025-40063 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2025-40063 and fix it if it is affected.

What it is: CVE-2025-40063 is a high-severity memory corruption vulnerability in Linux, published on 28 Oct 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-2025-40063 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-2025-40063/ (Markdown: https://insights.sbomify.com/CVE-2025-40063/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-40063
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-40063
- OSV: https://osv.dev/vulnerability/CVE-2025-40063

---
From sbomify Insights: https://insights.sbomify.com/CVE-2025-40063/
Summaries are generated and may contain mistakes; the official description above is the record.