---
id: CVE-2026-71847
title: Ruby JSON is a JSON implementation for Ruby
summary: >-
  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
  stora…
severity: low
cwe:
  - CWE-416
vendor: json
product: json
affected:
  - 'json >= 2.20.0, <= 2.21.1'
patched:
  - json 2.21.2
published: '2026-08-07'
updated: '2026-09-18'
sourceUpdated: '2026-09-18T20:05:53.723'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-71847'
references:
  - url: 'https://github.com/ruby/json/security/advisories/GHSA-9hj4-r449-hfvc'
    label: security-advisories@github.com
  - url: 'https://github.com/ruby/json/security/advisories/GHSA-9hj4-r449-hfvc'
    label: 134c704f-9b21-4f2e-91b3-4a467353bcc0
  - url: 'https://github.com/advisories/GHSA-9hj4-r449-hfvc'
tags:
  - nvd
  - ghsa
  - rubygems
epss: 0.00385
epssPercentile: 0.32496
aliases:
  - GHSA-9hj4-r449-hfvc
ecosystem: rubygems
ingestedAt: '2026-08-07T19:16:20.310Z'
---

## Overview

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

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.

## Package advisory (CVE-2026-71847)

Affected packages:

- `json >= 2.20.0, <= 2.21.1`

Patched in:

- `json 2.21.2`

Source: https://github.com/advisories/GHSA-9hj4-r449-hfvc