[DRE-maint] Bug#1143948: ruby-json: CVE-2026-71847

[Salvatore Bonaccorso]

Source: ruby-json
Version: 2.21.1+dfsg-1
Severity: important
Tags: security upstream
X-Debbugs-Cc: carnil at debian.org, Debian Security Team <team at security.debian.org>

Hi,

The following vulnerability was published for ruby-json.

CVE-2026-71847[0]:
| 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.


If you fix the vulnerability please also make sure to include the
CVE (Common Vulnerabilities & Exposures) id in your changelog entry.

For further information see:

[0] https://security-tracker.debian.org/tracker/CVE-2026-71847
    https://www.cve.org/CVERecord?id=CVE-2026-71847
[1] https://github.com/ruby/json/security/advisories/GHSA-9hj4-r449-hfvc
[2] https://github.com/ruby/json/commit/2c332bfe2bfb0e754da07e2a0310ef106bf46482

Please adjust the affected versions in the BTS as needed.

Regards,
Salvatore