CVE-2026-71847

Name	CVE-2026-71847
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 (at NVD; CERT, ENISA, LWN, oss-sec, fulldisc, Debian ELTS, Red Hat, Ubuntu, Gentoo, SUSE bugzilla/CVE, GitHub advisories/code/issues, web search, more)

Vulnerable and fixed packages

The table below lists information on source packages.

Source Package	Release	Version	Status
ruby-json (PTS)	bookworm	2.6.3+dfsg-1	fixed
	trixie	2.9.1+dfsg-1	fixed
	forky, sid	3.0.2+dfsg-1	fixed

The information below is based on the following data on fixed versions.

Package	Type	Release	Fixed Version	Urgency	Origin	Debian Bugs
ruby-json	source	(unstable)	(not affected)

Notes

- ruby-json <not-affected> (Vulnerable code never in a Debian released version, bug #1143948)
https://github.com/ruby/json/security/advisories/GHSA-9hj4-r449-hfvc
Introduced with https://github.com/ruby/json/commit/4bd1e9bce64c82b6e829f4583a62bab485529a00 (v2.20.0)
Fixed by: https://github.com/ruby/json/commit/2c332bfe2bfb0e754da07e2a0310ef106bf46482 (v2.21.2)