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CVE-2026-71847— Ruby JSON: JSON::ResumableParser#partial_value dereferences a freed input buffer and crashes on truncated duplicate-key streams

Quick assessment

Affected
ruby json
Exploitation
Public or AI PoC available; prioritize validation
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Ruby json是Ruby组织的一款处理JSON数据的软件。 Ruby json 2.20.0版本至2.21.2之前版本存在资源管理错误漏洞，该漏洞源于Ruby JSON原生C扩展在清除已消费的JSON::ResumableParser输入缓冲区后，state.start、state.cursor和state.end仍指向已释放的存储，导致处理包含重复键的不完整对象时发生堆释放后重用，攻击者通过向使用JSON::ResumableParser的应用程序提供恶意JSON流数据，可导致进程终止。

CVSS 8.7 · High EPSS 0.39% · P32

Possible ATT&CK Techniques 1 AI

T1068 · Exploitation for Privilege Escalation

Affected Version Matrix 1

VendorProduct Version RangeStatus
ruby json >= 2.20.0, < 2.21.2 affected
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I. Basic Information for CVE-2026-71847

Vulnerability Information
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Vulnerability Title
Ruby JSON: JSON::ResumableParser#partial_value dereferences a freed input buffer and crashes on truncated duplicate-key streams
Source: CVE Program / CVE List V5
Vulnerability 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.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
Source: CVE Program / CVE List V5
Vulnerability Type
释放后使用
Source: CVE Program / CVE List V5
Vulnerability Title
Ruby json 资源管理错误漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Ruby json是Ruby组织的一款处理JSON数据的软件。 Ruby json 2.20.0版本至2.21.2之前版本存在资源管理错误漏洞，该漏洞源于Ruby JSON原生C扩展在清除已消费的JSON::ResumableParser输入缓冲区后，state.start、state.cursor和state.end仍指向已释放的存储，导致处理包含重复键的不完整对象时发生堆释放后重用，攻击者通过向使用JSON::ResumableParser的应用程序提供恶意JSON流数据，可导致进程终止。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
ruby json >= 2.20.0, < 2.21.2 -

II. Public POCs for CVE-2026-71847

# POC Description Source Link Shenlong Link
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Qwen3.6-35B-A3B · 7455 chars
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III. Intelligence Information for CVE-2026-71847

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Vendor Advisories for CVE-2026-71847 (1)

IV. Related Vulnerabilities

Same product: json
Same vendor: ruby
Same weakness: CWE-416

V. Comments for CVE-2026-71847

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