# CVE-2025-12875: mruby array.c ary_fill_exec out-of-bounds write

> Local attackers can exploit an out-of-bounds write in mruby's array fill function to potentially execute arbitrary code or escalate privileges.

- **Severity:** Medium 4.8 (`CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:L/VI:L/VA:L/SC:N/SI:N/SA:N/E:P`)
- **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:** No
- **Published:** 7 Nov 2025
- **Updated:** 24 Feb 2026
- **Also known as:** GHSA-q269-xqww-45mm, UBUNTU-CVE-2025-12875

## What is CVE-2025-12875?

CVE-2025-12875 is a medium-severity memory corruption vulnerability in mruby, published on 7 Nov 2025. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

A weakness has been identified in mruby 3.4.0. This vulnerability affects the function ary_fill_exec of the file mrbgems/mruby-array-ext/src/array.c. Executing a manipulation of the argument start/length can lead to out-of-bounds write. The attack needs to be launched locally. The exploit has been made available to the public and could be used for attacks. This patch is called 93619f06dd378db6766666b30c08978311c7ec94. It is best practice to apply a patch to resolve this issue.

Weakness: CWE-787 (Out-of-bounds Write), CWE-119 (Improper Restriction of Operations within the Bounds of a Memory Buffer)

## Which versions are affected by CVE-2025-12875?

It affects 1 product.


Products: Mruby Mruby.

## How do I fix CVE-2025-12875?

No fix has been published for CVE-2025-12875 yet. Limit exposure of the affected software until one is available.

## Is CVE-2025-12875 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2025-12875 exists.

## Other vulnerabilities in mruby

- [CVE-2020-6838](https://insights.sbomify.com/CVE-2020-6838/): Use after free in n/a (critical 9.8)
- [CVE-2020-6839](https://insights.sbomify.com/CVE-2020-6839/): Memory corruption in n/a (critical 9.8)
- [CVE-2020-6840](https://insights.sbomify.com/CVE-2020-6840/): Use after free in n/a (critical 9.8)
- [CVE-2018-10199](https://insights.sbomify.com/CVE-2018-10199/): Use after free in n/a (critical 9.8)
- [CVE-2022-1212](https://insights.sbomify.com/CVE-2022-1212/): Use-After-Free in str_escape in mruby/mruby in mruby/mruby (critical 9.3)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2025-12875 and fix it if it is affected.

What it is: CVE-2025-12875 is a medium-severity memory corruption vulnerability in mruby, published on 7 Nov 2025. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2025-12875 exists.

Affected product: mruby. 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-2025-12875/ (Markdown: https://insights.sbomify.com/CVE-2025-12875/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-12875
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-12875
- OSV: https://osv.dev/vulnerability/CVE-2025-12875

---
From sbomify Insights: https://insights.sbomify.com/CVE-2025-12875/
Summaries are generated and may contain mistakes; the official description above is the record.