CVE-2026-25586Public exploitNetwork attack vector

Sandbox escape via shadowed hasOwnProperty check

Published Feb 6, 2026 · Updated Feb 6, 2026

Prototype-whitelist bypass in nyariv SandboxJS before 0.8.29 allows attackers to escape the sandbox through crafted JavaScript. The property-access path calls a sandbox object's shadowable hasOwnProperty method and skips prototype whitelist checks when attacker code makes it return true. Default Sandbox configuration is affected, allowing access to blocked properties such as proto, pollution of host Object.prototype, and persistent impact across sandboxes.

CVSS severity10.0
Critical
EPSS probability0.65%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Prototype-whitelist bypass in nyariv SandboxJS before 0.8.29 allows attackers to escape the sandbox through crafted JavaScript. The property-access path calls a sandbox object's shadowable hasOwnProperty method and skips prototype whitelist checks when attacker code makes it return true. Default Sandbox configuration is affected, allowing access to blocked properties such as proto, pollution of host Object.prototype, and persistent impact across sandboxes.

The record

CVE
CVE-2026-25586
Published
Feb 6, 2026
Updated
Feb 6, 2026
Vendor
nyariv
Product
SandboxJS
Classifications
CWE-74
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Feb 6, 2026CVE publishedPublication date reported by the CVE source.
  2. Feb 6, 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=< 0.8.29

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

nyariv · SandboxJSversion=< 0.8.29

Published CVSS scores

10.0GitHub, Inc.CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/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)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-74Improper Neutralization of Special Elements in Output Used by a Downstream Component ('Injection')

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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