CVE-2025-34146Public exploit

Sandbox escape via unchecked function prototype access

Published Jul 31, 2025 · Updated Jun 23, 2026

Prototype pollution in nyariv SandboxJS 0.8.23 and earlier allows local users to modify Object.prototype via crafted JavaScript. The executor's function-property branch treats an inherited proto lookup as unowned and skips SandboxError, while the parser misses constructor-created functions. Exploitation requires crafted code to run through an embedding application; polluted host objects can crash the process or permit execution outside the sandbox.

CVSS severity7.0
High
EPSS probability0.20%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Prototype pollution in nyariv SandboxJS 0.8.23 and earlier allows local users to modify Object.prototype via crafted JavaScript. The executor's function-property branch treats an inherited proto lookup as unowned and skips SandboxError, while the parser misses constructor-created functions. Exploitation requires crafted code to run through an embedding application; polluted host objects can crash the process or permit execution outside the sandbox.

The record

CVE
CVE-2025-34146
Published
Jul 31, 2025
Updated
Jun 23, 2026
Vendor
nyariv
Product
SandboxJS
Classifications
CWE-1321, CAPEC-77, T1059.007
Attack vector
local
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jul 31, 2025CVE publishedPublication date reported by the CVE source.
  2. Jun 23, 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?

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

  1. Affected versionversion=0 <=0.8.23

What conditions does exploitation require?

Attack vectorlocal
Required privilegesunauthenticated

What is affected?

nyariv · SandboxJSversion=0 <=0.8.23

Published CVSS scores

7.0VulnCheckCVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:H/SC:N/SI:N/SA:N

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.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

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-1321Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution')
CAPEC-77Manipulating User-Controlled Variables
T1059.007JavaScript/JScript

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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