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Sandboxjs CVE-2026-25586

CRITICAL
Improper Neutralization of Special Elements in Output Used by a Downstream Component ('Injection') (CWE-74)
2026-02-06 security-advisories@github.com GHSA-jjpw-65fv-8g48
Information Disclosure Sandboxjs
10.0
CVSS 3.1 · GitHub Advisory
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Severity by source

GitHub Advisory PRIMARY
10.0 CRITICAL
AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H

Primary rating from GitHub Advisory · only source for this CVE.

CVSS VectorGitHub Advisory

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H
Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Changed
Confidentiality
High
Integrity
High
Availability
High

Lifecycle Timeline

4
Analysis Generated
Mar 12, 2026 - 21:54 vuln.today
PoC Detected
Feb 18, 2026 - 14:32 vuln.today
Public exploit code
Patch released
Feb 18, 2026 - 14:32 nvd
Patch available
CVE Published
Feb 06, 2026 - 20:16 nvd
CRITICAL 10.0

DescriptionGitHub Advisory

SandboxJS is a JavaScript sandboxing library. Prior to 0.8.29, a sandbox escape is possible by shadowing hasOwnProperty on a sandbox object, which disables prototype whitelist enforcement in the property-access path. This permits direct access to __proto__ and other blocked prototype properties, enabling host Object.prototype pollution and persistent cross-sandbox impact. This vulnerability is fixed in 0.8.29.

AnalysisAI

SandboxJS has a third CVSS 10.0 sandbox escape via Map prototype shadowing that allows complete sandbox bypass.

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Attack ChainAIDerived

Hypothetical attack flow derived from CVE metadata

Access
Shadow hasOwnProperty on sandbox object
Delivery
Bypass prototype whitelist enforcement
Exploit
Access __proto__ and blocked properties
Execution
Pollute host Object.prototype
Impact
Execute code across sandboxes
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Vulnerability AssessmentAI

Exploitation SandboxJS version prior to 0.8.29 with default sandbox configuration allowing user-controlled object manipulation and property shadowing without input validation. Additional conditions and limiting factors are described in the full assessment.
Risk Assessment CVSS 10.0 with PoC and patch. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in.
Exploit Scenario An attacker shadows Map prototype methods to break out of the sandbox and execute arbitrary code in the host environment.
Remediation Update to 0.8.29+. … Detailed patch versions, workarounds, and compensating controls in full report.
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Recommended ActionAI

Within 24 hours: Identify all instances of SandboxJS in use across the organization and their version numbers; communicate findings to development and operations teams. …

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CVE-2026-25586 vulnerability details – vuln.today
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