CVE-2026-25881: @nyariv/sandboxjs has host prototype pollution from sandbox via array intermediary (sandbox escape)

Severity: critical (CVSS 10.0 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.6% probability of exploitation in the next 30 days
Public exploit or detection template: yes
Published: 2026-02-09 · updated 2026-06-17
Weakness: CWE-1321

Description

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.

Affected products

nyariv SandboxJS: before 0.8.31 — fixed in 0.8.31

How to fix

Upgrade to a fixed version: nyariv SandboxJS 0.8.31. Check the vendor advisory for mitigations.

References

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