CVE-2026-33210: Ruby-Lang JSON

Critical severity, CVSS 9.1. EPSS: 1% chance of exploitation in the next 30 days.

Ruby JSON is a JSON implementation for Ruby. From version 2.14.0 to before versions 2.15.2.1, 2.17.1.2, and 2.19.2, a format string injection vulnerability can lead to denial of service attacks or information disclosure, when the allow_duplicate_key: false parsing option is used to parse user supplied documents. This issue has been patched in versions 2.15.2.1, 2.17.1.2, and 2.19.2.

Affected products

• Ruby-Lang JSON: from 2.14.0, before 2.15.2.1 (fixed in 2.15.2.1); from 2.16.0, before 2.17.1.2 (fixed in 2.17.1.2); from 2.18.0, before 2.19.2 (fixed in 2.19.2)

Published 2026-03-20. Last modified 2026-08-21.