Ruby JSON has a format string injection vulnerability

GHSA-3m6g-2423-7cp3 · CVE-2026-33210

Published Mar 19, 2026 · Modified Sep 10, 2026

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Description

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.

Patches

Patched in 2.19.2.

Workarounds

The issue can be avoided by not using the allow_duplicate_key: false parsing option.

References

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

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