CVE-2026-33210: Ruby JSON has a format string injection vulnerability

March 19, 2026 (updated March 25, 2026)

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.

References

github.com/advisories/GHSA-3m6g-2423-7cp3
github.com/ruby/json
github.com/ruby/json/security/advisories/GHSA-3m6g-2423-7cp3
github.com/rubysec/ruby-advisory-db/blob/master/gems/json/CVE-2026-33210.yml
nvd.nist.gov/vuln/detail/CVE-2026-33210

Code Behaviors & Features

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