PyPI/ujson CVE-2026-54911: medium 6.5, EPSS 0.37%

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

Action: Upgrade ujson to 5.13.0 or later.

pip install ujson==5.13.0

Affected

Fixed versions

Sources

• osv: PYSEC-2026-2294
• https://github.com/ultrajson/ultrajson/releases/tag/5.13.0
• https://github.com/ultrajson/ultrajson/commit/169eaf36b1116fece5034ee79a7a0ef3f6deedcf
• https://github.com/ultrajson/ultrajson/security/advisories/GHSA-3j69-69wj-xqx2

CVE-2026-54911 · published 2026-06-22T22:16:50.397Z · modified 2026-07-13T07:15:45.403361942Z · JSON