CVE-2026-34208 CRITICAL

CVE-2026-34208: SandboxJS: Sandbox integrity escape

Vendor Nyariv
Product SandboxJS
Weakness CWE-693
Published April 6, 2026
Last update April 6, 2026

CVSS base score

10.0/10
Attack vector Network
Attack complexity Low
Privileges required None
User interaction None
Confidentiality High
Integrity High

CVSS vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:L

What the vulnerability does

01Description

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.

Key dates

02Disclosure timeline

April 6, 2026 CVE published
April 6, 2026 Record updated