---
cve: "CVE-2026-54911"
severity: "MEDIUM"
cvss: 6.5
epss: "0.4%"
vendor: "ultrajson"
kev: false
exploited: false
published: "2026-06-22 22:16:50"
tags: [cve, security, medium]
source: tsecurity.de CVE-Dossier
exported: "2026-09-20T20:04:21+02:00"
---

# CVE-2026-54911

> 6.5 MEDIUM · 🧪 PoC

## Beschreibung

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.

## CVSS-Vektor

```
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N
```

| Metrik | Wert | Bewertung |
|---|---|---|
| AV Angriffsvektor | Netzwerk | bad |
| AC Komplexität | Gering | bad |
| PR Privilegien | Keine | bad |
| UI Interaktion | Keine | bad |
| S Scope | Unverändert | good |
| C Vertraulichkeit | Gering | warn |
| I Integrität | Gering | warn |
| A Verfügbarkeit | Keine | good |

## Patch verfügbar (OSV)

- 1a23a68bbc5aff84e3f78f65011362cf3389693c (Commit)
- 169eaf36b1116fece5034ee79a7a0ef3f6deedcf (Commit)

## Referenzen

- <https://github.com/ultrajson/ultrajson/security/advisories/GHSA-3j69-69wj-xqx2>
- <https://github.com/ultrajson/ultrajson/commit/169eaf36b1116fece5034ee79a7a0ef3f6deedcf>
- <https://github.com/ultrajson/ultrajson/releases/tag/5.13.0>

---
_Exportiert aus dem [tsecurity.de CVE-Dossier](https://tsecurity.de/cve?cve=CVE-2026-54911) · Datenquellen: EUVD (ENISA), NVD, OSV, CISA KEV, FIRST EPSS, Exploit-DB, BSI BITS_