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CVE-2025-12875VulnerabilityPublished Updated

CVE-2025-12875: mruby · Out-of-bounds Write

Affects mrubySource CVE Database V5

0

Not known to be exploited · CVSS 4.8 Medium.

Data as of 26 Oct 2026, 06:26 UTC

CVSS 4.0 base score
4.8Medium
How severe the flaw is on the 0–10 CVSS scale.
EPSS
0.1% chance of exploitation in 30 days – higher than 6% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
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

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 7 Nov 2025

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponised: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 2026-10-26.

What to do

Affected software

ProductAffectedFixed in
GitHubmruby/mrubypkg:github/mruby/mrubyOther threatsAffected
  • =3.4.0
Fixed in–

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

To mitigate CVE-2025-12875, organizations should immediately apply the official patch identified by commit 93619f06dd378db6766666b30c08978311c7ec94 to all instances of mruby 3.4.0 in their environment. Beyond patching, restrict local access to systems running mruby to trusted users only, minimizing the risk of local exploitation. Employ strict access controls and monitoring on multi-user systems to detect suspicious local activity. Consider using application sandboxing or containerization to limit the impact of potential memory corruption. Regularly audit and update embedded systems or applications that include mruby to ensure they do not run vulnerable versions. If patching is delayed, implement host-based intrusion detection systems (HIDS) to monitor for exploitation attempts. Finally, educate developers and system administrators about the risks of local vulnerabilities and the importance of timely patch management in embedded scripting environments.

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.

References

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