Affected: ultrajson, Red Hat OpenStack Platform 16.2, Red Hat OpenStack Platform 17.1, Red Hat OpenStack Platform 18.0

UltraJSON is a fast JSON encoder and decoder written in pure C with bindings for Python 3.7+. Versions 5.4.0 through 5.11.0 contain an accumulating memory leak in JSON parsing large (outside of the range [-2^63, 2^64 - 1]) integers. The leaked memory is a copy of the string form of the integer plus an additional NULL byte. The leak occurs irrespective of whether the integer parses successfully or is rejected due to having more than sys.get_int_max_str_digits() digits, meaning that any sized leak per malicious JSON can be achieved provided that there is no limit on the overall size of the payload. Any service that calls ujson.load()/ujson.loads()/ujson.decode() on untrusted inputs is affected and vulnerable to denial of service attacks. This issue has been fixed in version 5.12.0.

Affected: Ubuntu:Pro:22.04:LTS: ujson, Ubuntu:Pro:24.04:LTS: ujson, Ubuntu:25.10: ujson, Ubuntu:26.04:LTS: ujson

Cameron Criswell discovered that UltraJSON contained a memory leak that would occur when parsing large integers. An attacker could possibly use this issue to cause UltraJSON to crash, resulting in a denial of service. This issue only affected Ubuntu 24.04 LTS, Ubuntu 25.10, and Ubuntu 26.04 LTS. (CVE-2026-32874)

It was discovered that UltraJSON contained integer overflow/underflow issues when calculating how much memory to reserve for indentation in certain instances. An attacker could possibly use this issue to cause UltraJSON to crash, resulting in a denial of service. (CVE-2026-32875)