PYSEC-2026-1057 Incorrect handling of invalid surrogate pair characters

Impact What kind of vulnerability is it? Who is impacted? Anyone parsing JSON from an untrusted source is vulnerable. JSON strings that contain escaped surrogate characters not part of a proper surrogate pair were decoded incorrectly. Besides corrupting strings, this allowed for potential key...

Potential double free of buffer during string decoding

ImpactWhat kind of vulnerability is it? Who is impacted?When an error occurs while reallocating the buffer for string decoding, the buffer gets freed twice.Due to how UltraJSON uses the internal decoder, this double free is impossible to trigger from Python. PatchesHas the problem been patched?...

Linux Distros Unpatched Vulnerability : CVE-2026-54911

The Linux/Unix host has one or more packages installed that are impacted by a vulnerability without a vendor supplied patch available. - 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...

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 rejectbytes=False option. When set, they may accept malformed or truncated UTF-8 byte sequences, silently rewriting them into different...

PYSEC-2026-2294

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 rejectbytes=False option. When set, they may accept malformed or truncated UTF-8 byte sequences, silently rewriting them into different...

DEBIAN-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 rejectbytes=False option. When set, they may accept malformed or truncated UTF-8 byte sequences, silently rewriting them into different...

UBUNTU-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 rejectbytes=False option. When set, they may accept malformed or truncated UTF-8 byte sequences, silently rewriting them into different...

CVE-2026-54911

CVE-2026-54911 (UltraJSON) : The vulnerability affects UltraJSON (C core with Python bindings) where ujson.dumps()/dump()/encode() with reject_bytes=False may accept malformed or truncated UTF-8, silently rewriting to other Unicode characters instead of rejecting. This enables input validation by...

CVE-2026-54911 UltraJSON: Malformed/Truncated UTF-8 Accepted and Silently Rewritten in ujson.dumps()

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 rejectbytes=False option. When set, they may accept malformed or truncated UTF-8 byte sequences, silently rewriting them into different...

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 rejectbytes=False option. When set, they may accept malformed or truncated UTF-8 byte sequences, silently rewriting them into different...

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 rejectbytes=False option. When set, they may accept malformed or truncated UTF-8 byte sequences, silently rewriting them into different...

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 rejectbytes=False option. When set, they may accept malformed or truncated UTF-8 byte sequences, silently rewriting them into different...

CVE-2026-54911 UltraJSON: Malformed/Truncated UTF-8 Accepted and Silently Rewritten in ujson.dumps()

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 rejectbytes=False option. When set, they may accept malformed or truncated UTF-8 byte sequences, silently rewriting them into different...

GHSA-3J69-69WJ-XQX2 UltraJSON: Malformed/Truncated UTF-8 Accepted and Silently Rewritten in ujson.dumps()

Summary ujson.dumps or ujson.dump or ujson.encode have a rejectbytes=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...

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

Summary ujson.dumps or ujson.dump or ujson.encode have a rejectbytes=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...

PT-2026-51093

Name of the Vulnerable Software and Affected Versions UltraJSON versions prior to 5.13.0 Description The functions ujson.dumps, ujson.dump, and ujson.encode contain an issue when the reject bytes variable is set to False. In this configuration, the software may accept malformed or truncated UTF-8...

CVE-2026-44660

A flaw was found in UltraJSON, a fast JSON encoder and decoder. When the ujson.dump function attempts to write data to a file-like object and an error occurs during this operation, the memory allocated for the serialized JSON string is not properly released. This continuous failure to deallocate...

Linux Distros Unpatched Vulnerability : CVE-2026-44660

The Linux/Unix host has one or more packages installed that are impacted by a vulnerability without a vendor supplied patch available. - UltraJSON is a fast JSON encoder and decoder written in pure C with bindings for Python 3.7+. Prior to 5.12.1, when ujson.dump writes to a file-like object and...

CVE-2026-44660

UltraJSON is a fast JSON encoder and decoder written in pure C with bindings for Python 3.7+. Prior to 5.12.1, when ujson.dump writes to a file-like object and the write operation raises an exception, the serialized JSON string object is not decremented, leaking memory. Each failed write operatio...

DEBIAN-CVE-2026-44660

UltraJSON is a fast JSON encoder and decoder written in pure C with bindings for Python 3.7+. Prior to 5.12.1, when ujson.dump writes to a file-like object and the write operation raises an exception, the serialized JSON string object is not decremented, leaking memory. Each failed write operatio...