CVE-2026-44660

EUVD-2026-32663
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.
ProviderTypeBase ScoreAtk. VectorAtk. ComplexityPriv. RequiredVector
GitHub_MCNA
8.7 HIGH
NETWORK
LOW
NONE
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
Base Score
CVSS 3.x
EPSS Score
Percentile: Unknown
Early Detection
Affected products identified ahead of NVD analysis through intelligence sources.
VendorProductVersionSource
ultrajson_projectultrajson
𝑥
< 5.12.1
CNA
Common Weakness Enumeration
References
https://github.com/ultrajson/ultrajson/commit/82af1d0ac01d09aa40c887b460d44b9d9f4bccd9
https://github.com/ultrajson/ultrajson/releases/tag/5.12.1
https://github.com/ultrajson/ultrajson/security/advisories/GHSA-c38f-wx89-p2xg