CVE-2025-70347Public exploit

Local crash via invalid persistent-bytecode heap traversal

Published Feb 10, 2026 · Updated Feb 10, 2026

Memory-safety error in MQuickJS before commit 54e0c6e allows local users to crash mqjs by compiling crafted JavaScript as 32-bit bytecode. After JS_PrepareBytecode64to32 returns the heap buffer as persistent bytecode, JS_FreeContext traverses that reused buffer as live heap blocks, and get_mblock_size reads an invalid address. The mqjs process must compile the crafted file with 32-bit bytecode output enabled; the demonstrated consequence is a segmentation fault, not code execution.

CVSS severity5.5
Medium
EPSS probability0.15%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Memory-safety error in MQuickJS before commit 54e0c6e allows local users to crash mqjs by compiling crafted JavaScript as 32-bit bytecode. After JS_PrepareBytecode64to32 returns the heap buffer as persistent bytecode, JS_FreeContext traverses that reused buffer as live heap blocks, and get_mblock_size reads an invalid address. The mqjs process must compile the crafted file with 32-bit bytecode output enabled; the demonstrated consequence is a segmentation fault, not code execution.

The record

CVE
CVE-2025-70347
Published
Feb 10, 2026
Updated
Feb 10, 2026
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-400, T1499.004
Attack vector
local
Privileges
unauthenticated

Timeline

How it unfolded

  1. Feb 10, 2026CVE publishedPublication date reported by the CVE source.
  2. Feb 10, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectorlocal
Required privilegesunauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

5.5CISA-ADPCVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-400Uncontrolled Resource Consumption
T1499.004Application or System Exploitation

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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