CVE-2026-44660
Published:May 27, 2026
Updated:June 13, 2026
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.
Affected Packages
ujson (CONDA):
Affected version(s) >=1.33 <5.12.1Fix Suggestion:
Update to version 5.12.1https://github.com/ultrajson/ultrajson.git (GITHUB):
Affected version(s) >=v1.19 <5.12.1Fix Suggestion:
Update to version 5.12.1ujson (PYTHON):
Affected version(s) >=1.4 <5.12.1Fix Suggestion:
Update to version 5.12.1ujson (PYTHON):
Affected version(s) >=1.4 <5.12.1Fix Suggestion:
Update to version 5.12.1Related Resources (5)
Do you need more information?
Contact UsCVSS v4
Base Score:
8.7
Attack Vector
NETWORK
Attack Complexity
LOW
Attack Requirements
NONE
Privileges Required
NONE
User Interaction
NONE
Vulnerable System Confidentiality
NONE
Vulnerable System Integrity
NONE
Vulnerable System Availability
HIGH
Subsequent System Confidentiality
NONE
Subsequent System Integrity
NONE
Subsequent System Availability
NONE
CVSS v3
Base Score:
7.5
Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality
NONE
Integrity
NONE
Availability
HIGH
Weakness Type (CWE)
Missing Release of Memory after Effective Lifetime
EPSS
Base Score:
0.05