Signal is active with 1 mentions in latest observed window
Recommended action window: Monitor and triage in normal cycle
NVD 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.
Priority
LOW
Exploitation
NONE
PoC
NONE
Patch
AVAILABLE
Momentum
STABLE
| Date | Total | Labels |
|---|
| 2026-08-08 | 1 | Disclosure1 |
| 2026-08-12 | 1 | Patch1 |
jet_ui v0.2.9 is out 🎉 - Security fixes: bump Rails to 8.1.3.1 (CVE-2026-66066) and json 2.21.2 (CVE-2026-71847) https://github.com/jetrockets/jet_ui #ruby #rails #rubyonrails #buildinpublic #devtools #jetrockets
Post summary
This tweet announces a new release that includes security patches for CVE-2026-66066 and CVE-2026-71847, but does not provide technical details or evidence of exploitation.
🚨HIGH - Ruby json C ext ResumableParser Heap Use-After-Free DoS (CVE-2026-71847) Ruby's json native C extension JSON::ResumableParser can leave start/cursor/end pointing to freed input after buffer clear; when partial_value rebuilds an incomplete object w/ duplicate keys, the warning path hits cursor_position and dereferences stale pointers, triggering heap UAF and crashing Ruby. Non-streamed JSON parsing is not affected. 👉Affected: json < 2.21.2 | Upgrade to 2.21.2
Post summary
The post announces CVE-2026-71847, outlining a heap use‑after‑free in Ruby's json ResumableParser and recommends upgrading to version 2.21.2.