CVE-2026-44660 HIGH

CVE-2026-44660: UltraJSON: Memory Leak in ujson.dump() on Write Failure

Vendor Ultrajson
Product ultrajson
Weakness CWE-401
Published May 27, 2026
Last update May 30, 2026
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CVSS base score

8.7/10
Attack vector Network
Attack complexity Low
Privileges required None
User interaction None
Confidentiality —
Integrity —

CVSS 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

What the vulnerability does

01Description

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.

Key dates

02Disclosure timeline

May 27, 2026 CVE published
May 30, 2026 Record updated