CVE-2026-34208: Nyariv Sandboxjs

Critical severity, CVSS 10.0. EPSS: 0.6% chance of exploitation in the next 30 days.

SandboxJS is a JavaScript sandboxing library. Prior to 0.8.36, SandboxJS blocks direct assignment to global objects (for example Math.random = ...), but this protection can be bypassed through an exposed callable constructor path: this.constructor.call(target, attackerObject). Because this.constructor resolves to the internal SandboxGlobal function and Function.prototype.call is allowed, attacker code can write arbitrary properties into host global objects and persist those mutations across sandbox instances in the same process. This vulnerability is fixed in 0.8.36.

Affected products

• Nyariv Sandboxjs: before 0.8.36 (fixed in 0.8.36)

Published 2026-04-06. Last modified 2026-06-17.