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Sandboxjs CVE-2026-25881

CRITICAL
Improperly Controlled Modification of Object Prototype Attributes (Prototype Pollution) (CWE-1321)
2026-02-09 security-advisories@github.com GHSA-ww7g-4gwx-m7wj
RCE Sandboxjs
9.0
CVSS 3.1 · GitHub Advisory
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Severity by source

GitHub Advisory PRIMARY
9.0 CRITICAL
AV:N/AC:H/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:H/PR:N/UI:N/S:C/C:H/I:H/A:H
Attack Vector
Network
Attack Complexity
High
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 - 18:07 vuln.today
Public exploit code
Patch released
Feb 18, 2026 - 18:07 nvd
Patch available
CVE Published
Feb 09, 2026 - 22:16 nvd
CRITICAL 9.0

DescriptionGitHub Advisory

SandboxJS is a JavaScript sandboxing library. Prior to 0.8.31, a sandbox escape vulnerability allows sandboxed code to mutate host built-in prototypes by laundering the isGlobal protection flag through array literal intermediaries. When a global prototype reference (e.g., Map.prototype, Set.prototype) is placed into an array and retrieved, the isGlobal taint is stripped, permitting direct prototype mutation from within the sandbox. This results in persistent host-side prototype pollution and may enable RCE in applications that use polluted properties in sensitive sinks (example gadget: execSync(obj.cmd)). This vulnerability is fixed in 0.8.31.

AnalysisAI

SandboxJS prior to 0.8.31 has yet another sandbox escape via prototype pollution, the sixth distinct escape technique discovered.

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Attack ChainAIDerived

Hypothetical attack flow derived from CVE metadata

Access
Place global prototype in array literal
Delivery
Retrieve prototype stripping isGlobal flag
Exploit
Mutate host built-in prototype
Execution
Pollute sensitive properties
Impact
Execute arbitrary code via gadget chains
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Vulnerability AssessmentAI

Exploitation SandboxJS versions prior to 0.8.31 with sandboxed JavaScript code execution enabled. … Additional conditions and limiting factors are described in the full assessment.
Risk Assessment CVSS 9.0 with PoC and patch. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in.
Exploit Scenario An attacker uses prototype pollution to escape the sandbox and execute code in the host environment.
Remediation Update to 0.8.31+. … Detailed patch versions, workarounds, and compensating controls in full report.
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Recommended ActionAI

Within 24 hours: Identify all applications and services using SandboxJS and determine current versions in production; assess whether untrusted or user-supplied code is executed in these sandboxes. …

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CVE-2026-25881 vulnerability details – vuln.today
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