CVE-2026-54911

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.

• CWE-20

• https://github.com/ultrajson/ultrajson/commit/169eaf36b1116fece5034ee79a7a0ef3f6deedcfPatch
• https://github.com/ultrajson/ultrajson/releases/tag/5.13.0Product, Release Notes
• https://github.com/ultrajson/ultrajson/security/advisories/GHSA-3j69-69wj-xqx2Mitigation, Patch, Vendor Advisory

Published

Jun 22, 2026

Last Modified

Jun 26, 2026

Status

Analyzed

• How Strix found a critical auth bypass in etcdStrix autonomously discovered a critical authentication bypass in etcd, later designated CVE-2026-33413.
• Autonomous PentestingAI agents that find and validate exploitable vulnerabilities like this one across your applications.
• PR ReviewsPentest every pull request so vulnerable code is caught before it ships to production.
• AI Penetration TestingHow AI-driven penetration testing continuously covers your attack surface.

• CVE-2026-54905concurrent-ruby is a modern concurrency tools for Ruby. Prio…5.5
• CVE-2026-54906concurrent-ruby is a modern concurrency tools for Ruby. Prio…9.8
• CVE-2026-54908Pion DTLS is a Go implementation of Datagram Transport Layer…6.3
• CVE-2026-54909pion/stun is a Go implementation of STUN. Prior to 3.1.3, XO…5.3
• CVE-2026-5491DriveLock Directory Traversal Information Disclosure Vulnera…7.5
• CVE-2026-54910FileBrowser Quantum is a free, self-hosted, web-based file m…7.7
• CVE-2026-54917SeaweedFS is a distributed storage system for object storage…10
• CVE-2026-54919cpp-httplib is a C++11 single-file header-only cross platfor…7.4
• CVE-2026-5492DriveLock Directory Traversal Information Disclosure Vulnera…6.5
• CVE-2026-5493Labcenter Electronics Proteus PDSPRJ File Parsing Out-Of-Bou…7.8
• CVE-2026-5494Labcenter Electronics Proteus PDSPRJ File Parsing Out-Of-Bou…7.8
• CVE-2026-5495Labcenter Electronics Proteus PDSPRJ File Parsing Out-Of-Bou…7.8