CVE-2026-32874

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.

CVSS v3 7.5 HIGH

7.5^/10

CVSS v3 : HIGH

Vector :

Exploitability : 3.9 / Impact : 3.6

Attack Vector NETWORK

Attack Complexity LOW

Privileges Required NONE

User Interaction NONE

Confidentiality Impact NONE

Integrity Impact NONE

Availability Impact HIGH

Scope UNCHANGED

References

Link	Resource
https://github.com/ultrajson/ultrajson/commit/4baeb950df780092bd3c89fc702a868e99a3a1d2	Patch
https://github.com/ultrajson/ultrajson/releases/tag/5.12.0	Product Release Notes
https://github.com/ultrajson/ultrajson/security/advisories/GHSA-wgvc-ghv9-3pmm	Vendor Advisory

Configurations

Configuration 1 (hide)

cpe:2.3:a:ultrajson_project:ultrajson:*:*:*:*:*:python:*:*

History

No history.

Information

Published : 2026-03-20 02:16

Updated : 2026-03-23 15:27

NVD link : CVE-2026-32874

Mitre link : CVE-2026-32874

CVE.ORG link : CVE-2026-32874

JSON object : View

Products Affected

ultrajson_project

ultrajson

CWE

CWE-401

Missing Release of Memory after Effective Lifetime

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