Critical severity · published Feb 6, 2026
CVE-2026-25586
SandboxJS has a Sandbox Escape via Prototype Whitelist Bypass and Host Prototype Pollution
10.0
CVSS
0.7%
EPSS
No
On KEV
Description
SandboxJS is a JavaScript sandboxing library. Prior to 0.8.29, a sandbox escape is possible by shadowing hasOwnProperty on a sandbox object, which disables prototype whitelist enforcement in the property-access path. This permits direct access to __proto__ and other blocked prototype properties, enabling host Object.prototype pollution and persistent cross-sandbox impact. This vulnerability is fixed in 0.8.29.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Confidentiality
High
Integrity
High
Availability
High
Scope
Changed
Exploitation
Is it being used?
Exploit prediction (EPSS)0.7% · higher than 53% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
SA
SandboxJS · nyariv
< 0.8.29 · source: vendor, NVD
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-25586
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-25586
Patch
https://github.com/nyariv/SandboxJS/commit/67cb186c41c78c51464f70405504e8ef0a6e43c3
Exploit
https://github.com/nyariv/SandboxJS/security/advisories/GHSA-jjpw-65fv-8g48
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