CVE-2026-71847
Ruby JSON: JSON::ResumableParser#partial_value dereferences a freed input buffer and crashes on truncated duplicate-key streams
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Description
Ruby JSON is a JSON implementation for Ruby. From 2.20.0 until 2.21.2, Ruby's JSON native C extension clears the consumed JSON::ResumableParser input buffer but leaves state.start, state.cursor, and state.end pointing into released storage. When partial_value reconstructs an incomplete object containing duplicate keys, the duplicate-key warning path calls cursor_position, which dereferences those stale pointers. This results in a heap-use-after-free and can terminate the Ruby process. An attacker who can supply JSON stream data to an application using JSON::ResumableParser may cause process termination when the application calls partial_value on incomplete attacker-controlled input containing duplicate object keys. This issue has been fixed in version 2.21.2.
Remediation
No guide yetNo remediation guidance has been written for this CVE yet, and no fixed version or vendor advisory is recorded against it.
References (1)
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