CVE-2025-12875Public exploit

Local interpreter crash via negative array-fill index

Published Nov 7, 2025 · Updated Nov 7, 2025

Out-of-bounds write in mruby 3.4.0 allows local users to crash the interpreter via a negative Array#__fill_exec start index. ary_fill_exec accepts a negative start without validation, forms a pointer before the array buffer, and writes length elements through it. Execution requires local users to run crafted Ruby code that calls the internal array-fill method; the published proof of concept aborts the process.

CVSS severity7.8
High
EPSS probability0.16%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Out-of-bounds write in mruby 3.4.0 allows local users to crash the interpreter via a negative Array#__fill_exec start index. ary_fill_exec accepts a negative start without validation, forms a pointer before the array buffer, and writes length elements through it. Execution requires local users to run crafted Ruby code that calls the internal array-fill method; the published proof of concept aborts the process.

The record

CVE
CVE-2025-12875
Published
Nov 7, 2025
Updated
Nov 7, 2025
Vendor
mruby
Product
mruby
Classifications
CWE-787
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Nov 7, 2025CVE publishedPublication date reported by the CVE source.
  2. Nov 7, 2025Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=3.4.0

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

mruby · mrubyversion=3.4.0

Published CVSS scores

5.3UbuntuCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:L
5.3VulDB CNACVSS:3.0/AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:L/E:P/RL:O/RC:C
7.8NIST NVDCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
5.3VulDB CNACVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:L/E:P/RL:O/RC:C
4.3VulDB CNAAV:L/AC:L/Au:S/C:P/I:P/A:P/E:POC/RL:OF/RC:C
4.8VulDB CNACVSS: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

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

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No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-787Out-of-bounds Write

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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