Use After Free Affecting json package, versions >=2.20.0, <2.21.2
Threat Intelligence
The probability is the direct output of the EPSS model, and conveys an overall sense of the threat of exploitation in the wild. The percentile measures the EPSS probability relative to all known EPSS scores. Note: This data is updated daily, relying on the latest available EPSS model version. Check out the EPSS documentation for more details.
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Test your applications- Snyk IDSNYK-RUBY-JSON-18599450
- published9 Aug 2026
- disclosed7 Aug 2026
- creditUnknown
Introduced: 7 Aug 2026
NewCVE-2026-71847 (opens in a new tab)How to fix?
Upgrade json to version 2.21.2 or higher.
Overview
json is a JSON implementation as a Ruby extension in C.
Affected versions of this package are vulnerable to Use After Free through JSON::ResumableParser#partial_value in ext/json/ext/parser/parser.c. An attacker can crash the Ruby process by supplying truncated streaming JSON with duplicate object keys and causing the application to call partial_value on the incomplete parse. The vulnerable warning path computes a cursor position for resumable-parser deprecation messages after the parser has already cleared and released its input buffer, leaving stale pointers in state.start, state.cursor, and state.end. When that duplicate-key path runs, it dereferences freed memory and terminates the process.