CVE-2026-44660
HIGHUltraJSON: Memory Leak in ujson.dump() on Write Failure
Title source: cnaDescription
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.
References (3)
Core 3
Core References
X_Refsource_Confirm x_refsource_confirm
https://github.com/ultrajson/ultrajson/security/advisories/GHSA-c38f-wx89-p2xg
X_Refsource_Misc x_refsource_misc
https://github.com/ultrajson/ultrajson/commit/82af1d0ac01d09aa40c887b460d44b9d9f4bccd9
X_Refsource_Misc x_refsource_misc
https://github.com/ultrajson/ultrajson/releases/tag/5.12.1
Scores
CVSS v3
7.5
EPSS
0.0037
EPSS Percentile
29.0%
Attack Vector
NETWORK
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
CISA SSVC
Vulnrichment
Exploitation
poc
Automatable
yes
Technical Impact
partial
Details
CWE
CWE-401
Status
published
Products (3)
pypi/ujson
0 - 5.12.1PyPI
ultrajson/ultrajson
< 5.12.1
ultrajson_project/ultrajson
< 5.12.1
Published
May 27, 2026
Tracked Since
May 28, 2026