Back to feed
EUVD-2026-38362 · Published Jun 22, 2026
UltraJSON is a fast JSON encoder and decoder written in pure C with bindings for Python 3.7+. Prior to 5.13.0, ujson.dumps() (or ujson.dump() or ujson.encode()) have a reject_bytes=False option. When set, they may accept malformed or truncated UTF-8 byte sequences, silently rewriting them into different Unicode characters instead of rejecting them. This leads to input validation bypass and data integrity issues. This vulnerability is fixed in 5.13.0.
Technologies
Ultrajson_Project Ultrajson
Weaknesses
CWE-20
CVSS scores
- v3.16.5
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N
MITRE ATT&CK
InferredWhere this vulnerability fits in an attack
Initial Access
References
Potentially impacted assets
See if this affects your attack surface
