CVE-2026-44660

UltraJSON: Memory Leak in ujson.dump() on Write Failure

Published May 27, 2026 CVSS 4.0 · 8.7 High EPSS < 1% KEV · Not listed
Description
UltraJSON is a fast JSON encoder and decoder written in pure C with bindings for Python 3.7+. Prior to 5.12.1, when ujson.dump() writes to a file-like object and the write operation raises an exception, the serialized JSON string object is not decremented, leaking memory. Each failed write operation leaks the full size of the serialized payload. This vulnerability is fixed in 5.12.1.

Remediation

No solution or workaround provided in the CVE record

Tracking

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Advisories

Source ID Title
Github GHSA Github GHSA GHSA-c38f-wx89-p2xg UltraJSON has a Memory Leak in ujson.dump() on Write Failure
History
Type Values Removed Values Added
First Time appeared Ultrajson Project
Ultrajson Project ultrajson
CPEs cpe:2.3:a:ultrajson_project:ultrajson:*:*:*:*:*:python:*:*
Vendors & Products Ultrajson Project
Ultrajson Project ultrajson
Metrics cvssV3_1

{'score': 7.5, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H'}

Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'yes', 'Exploitation': 'poc', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Type Values Removed Values Added
First Time appeared Ultrajson
Ultrajson ultrajson
Vendors & Products Ultrajson
Ultrajson ultrajson
Type Values Removed Values Added
Description UltraJSON is a fast JSON encoder and decoder written in pure C with bindings for Python 3.7+. Prior to 5.12.1, when ujson.dump() writes to a file-like object and the write operation raises an exception, the serialized JSON string object is not decremented, leaking memory. Each failed write operation leaks the full size of the serialized payload. This vulnerability is fixed in 5.12.1.
Title UltraJSON: Memory Leak in ujson.dump() on Write Failure
Weaknesses CWE-401
References
Metrics cvssV4_0

{'score': 8.7, 'vector': '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'}

Weaknesses

Sources

Status
PUBLISHED
Assigner
GitHub_M
Published
Updated
May 30, 2026, 1:49 AM
Reserved
May 7, 2026, 4:20 PM
Status
Analyzed
Published
May 27, 2026, 9:16 PM
Modified
Jun 17, 2026, 10:51 AM
Severity
Moderate
Public date
May 27, 2026, 8:42 PM