CVE-2026-25641 CRITICAL

CVE-2026-25641: SandboxJS has a sandbox escape via TOCTOU bug on keys in property accesses

Vendor Nyariv
Product SandboxJS
Weakness CWE-367
Published February 6, 2026
Last update February 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:H

What the vulnerability does

01Description

SandboxJS is a JavaScript sandboxing library. Prior to 0.8.29, there is a sandbox escape vulnerability due to a mismatch between the key on which the validation is performed and the key used for accessing properties. Even though the key used in property accesses is annotated as string, this is never enforced. 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. This vulnerability is fixed in 0.8.29.

Key dates

02Disclosure timeline

February 6, 2026 CVE published
February 6, 2026 Record updated