Sandbox escape via array-literal taint loss
Published Feb 9, 2026 · Updated Feb 9, 2026
Prototype pollution in nyariv SandboxJS before 0.8.31 allows attackers to mutate host built-in prototypes through sandboxed code. The CreateArray operation in src/executor.ts calls valueOrProp on array items, stripping the Prop object's isGlobal flag before later writes reach the guard in src/utils.ts. Any application that executes untrusted JavaScript is exposed; persistent host mutation is direct, while command execution requires a host gadget that consumes a polluted property.
Summary
What happened
Prototype pollution in nyariv SandboxJS before 0.8.31 allows attackers to mutate host built-in prototypes through sandboxed code. The CreateArray operation in src/executor.ts calls valueOrProp on array items, stripping the Prop object's isGlobal flag before later writes reach the guard in src/utils.ts. Any application that executes untrusted JavaScript is exposed; persistent host mutation is direct, while command execution requires a host gadget that consumes a polluted property.
The record
- CVE
- CVE-2026-25881
- Published
- Feb 9, 2026
- Updated
- Feb 9, 2026
- Vendor
- nyariv
- Product
- SandboxJS
- Classifications
- CWE-1321
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Feb 9, 2026CVE publishedPublication date reported by the CVE source.
- Feb 9, 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.
- Affected versionversion=< 0.8.31
What conditions does exploitation require?
What is affected?
Published CVSS scores
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.
Weakness, pattern, technique
Public exploit references
- SandboxJS array-intermediary prototype-pollution PoCproof of concept · demonstrated
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Technologies
Your stack
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Your stack
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