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

UltraJSON: Malformed/Truncated UTF-8 Accepted and Silently Rewritten in ujson.dumps()

Action: Upgrade ujson to 5.13.0 or later.

pip install ujson==5.13.0

Affected

Fixed versions

Sources

• osv: GHSA-3j69-69wj-xqx2
• https://github.com/ultrajson/ultrajson/security/advisories/GHSA-3j69-69wj-xqx2
• https://nvd.nist.gov/vuln/detail/CVE-2026-54911
• https://github.com/ultrajson/ultrajson/commit/169eaf36b1116fece5034ee79a7a0ef3f6deedcf
• https://github.com/pypa/advisory-database/tree/main/vulns/ujson/PYSEC-2026-2294.yaml
• https://github.com/ultrajson/ultrajson
• https://github.com/ultrajson/ultrajson/releases/tag/5.13.0

CVE-2026-54911 · published 2026-06-19T20:47:43Z · modified 2026-09-10T03:50:55.310105853Z · JSON