What’s Vulnerable › Vulnerabilities

CVE-2026-25586: SandboxJS has a Sandbox Escape via Prototype Whitelist Bypass and Host Prototype Pollution

• Severity: critical (CVSS 10.0 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.7% probability of exploitation in the next 30 days
• Public exploit or detection template: yes
• Published: 2026-02-06 · updated 2026-06-17
• Weakness: CWE-74

Description

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.

Affected products

• nyariv SandboxJS: before 0.8.29 — fixed in 0.8.29

How to fix

Upgrade to a fixed version: nyariv SandboxJS 0.8.29. Check the vendor advisory for mitigations.

References

• https://github.com/nyariv/SandboxJS/commit/67cb186c41c78c51464f70405504e8ef0a6e43c3
• https://github.com/nyariv/SandboxJS/security/advisories/GHSA-jjpw-65fv-8g48
• https://github.com/nyariv/SandboxJS/security/advisories/GHSA-jjpw-65fv-8g48

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