Memory leak in ultrajson - CVE-2026-32874
Published: April 27, 2026
Vulnerability identifier: #VU128154
CSH Severity: Medium
CVSS v4: 8.7 [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]
CVE-ID: CVE-2026-32874
CWE-ID: CWE-401
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vulnerability details
The vulnerability allows a remote attacker to cause a denial of service.
The vulnerability exists due to missing release of memory after effective lifetime in the JSON parser when parsing large integer values in untrusted JSON input. A remote attacker can send a specially crafted JSON payload containing large integers to cause a denial of service.
The issue is triggered for integers outside the range [-2^63, 2^64 - 1], and the leak occurs even if parsing fails because the integer exceeds sys.get_int_max_str_digits().
Affected software
ultrajson
IBM Watson Speech Services Cartridge for IBM Cloud Pak for Data
Fedora
Ubuntu
ujson (Ubuntu package)
python-ujson
IBM Watson Speech Services Cartridge for IBM Cloud Pak for Data
Fedora
Ubuntu
ujson (Ubuntu package)
python-ujson
How to mitigate CVE-2026-32874
Install security update from vendor's website.
ultrajson - update to 5.12.0
IBM Watson Speech Services Cartridge for IBM Cloud Pak for Data - update to 5.3.1 Patch 5
ujson (Ubuntu package) - addressed in versions 5.1.0-1ubuntu0.1~esm2, 5.9.0-1ubuntu0.1~esm1, 5.10.0-1ubuntu0.1, 5.11.0-3ubuntu0.1
python-ujson - update to 5.8.0-2.el9
IBM Watson Speech Services Cartridge for IBM Cloud Pak for Data - update to 5.3.1 Patch 5
ujson (Ubuntu package) - addressed in versions 5.1.0-1ubuntu0.1~esm2, 5.9.0-1ubuntu0.1~esm1, 5.10.0-1ubuntu0.1, 5.11.0-3ubuntu0.1
python-ujson - update to 5.8.0-2.el9