Vulnerability in Nyariv Sandboxjs

CVE-2026-25586

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.

Published · last modified .

CVSS v3 metric

CVSS v3 base score 10.0 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H.

EPSS exploit prediction

EPSS: 0.007 (50.0th percentile), scored .

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 50th percentile — 50.0% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS trend (30 days)EPSS over the last 30 days for CVE-2026-25586: held from 0.006 to 0.007.

EPSS over last 30 days · oldest: 0.006 · newest: 0.007 · change: +0.000

Affected products

Weakness classification (CWE)

References

Frequently asked questions

What is CVE-2026-25586?
CVE-2026-25586 is a critical-severity vulnerability in Nyariv Sandboxjs, classified under Improper Neutralization of Special Elements in Output Used by a Downstream Component (Injection). CVSS score: 10.0/10. Published 2026-02-06.
How severe is CVE-2026-25586?
Critical severity. CVSS v3 base score is 10.0 out of 10.