Summary
Ruby JSON has a format string injection vulnerability
Workarounds
The issue can be avoided by not using the allow_duplicate_key: false parsing option.
Impact
A format string injection vulnerability than that 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 option isn't the default, if you didn't opt-in to use it, you are not impacted.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
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Patched in 2.19.2.
Frequently Asked Questions
- What is CVE-2026-33210? CVE-2026-33210 is a high-severity security vulnerability in json (rubygems), affecting versions >= 2.18.0, < 2.19.2. It is fixed in 2.19.2, 2.17.1.2, 2.15.2.1.
- Which versions of json are affected by CVE-2026-33210? json (rubygems) versions >= 2.18.0, < 2.19.2 is affected.
- Is there a fix for CVE-2026-33210? Yes. CVE-2026-33210 is fixed in 2.19.2, 2.17.1.2, 2.15.2.1. Upgrade to this version or later.
- Is CVE-2026-33210 exploitable, and should I be worried? Whether CVE-2026-33210 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether CVE-2026-33210 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix CVE-2026-33210?
- Upgrade
jsonto 2.19.2 or later - Upgrade
jsonto 2.17.1.2 or later - Upgrade
jsonto 2.15.2.1 or later
- Upgrade