Improper Input Validation Affecting ujson package, versions *


Severity

Recommended
low

Based on Debian security rating.

Threat Intelligence

EPSS
0.27% (19th percentile)

Do your applications use this vulnerable package?

In a few clicks we can analyze your entire application and see what components are vulnerable in your application, and suggest you quick fixes.

Test your applications
  • Snyk IDSNYK-DEBIAN12-UJSON-17429553
  • published23 Jun 2026
  • disclosed22 Jun 2026

Introduced: 22 Jun 2026

CVE-2026-54911  (opens in a new tab)
CWE-20  (opens in a new tab)

How to fix?

There is no fixed version for Debian:12 ujson.

NVD Description

Note: Versions mentioned in the description apply only to the upstream ujson package and not the ujson package as distributed by Debian. See How to fix? for Debian:12 relevant fixed versions and status.

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 Base Scores

version 3.1