OESA-2026-3606

UltraJSON (aka ujson) through 5.1.0 has a stack-based buffer overflow in Buffer_AppendIndentUnchecked (called from encode). Exploitation can, for example, use a large amount of indentation.(CVE-2021-45958)

UltraJSON is a fast JSON encoder and decoder written in pure C with bindings for Python 3.7+. Affected versions were found to improperly decode certain characters. 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 confusion and value overwriting in dictionaries. All users parsing JSON from untrusted sources are vulnerable. From version 5.4.0, UltraJSON decodes lone surrogates in the same way as the standard library's json module does, preserving them in the parsed output. Users are advised to upgrade. There are no known workarounds for this issue.(CVE-2022-31116)

UltraJSON is a fast JSON encoder and decoder written in pure C with bindings for Python 3.7+. In versions prior to 5.4.0 an error occurring while reallocating a buffer for string decoding can cause the buffer to get freed twice. Due to how UltraJSON uses the internal decoder, this double free is impossible to trigger from Python. This issue has been resolved in version 5.4.0 and all users should upgrade to UltraJSON 5.4.0. There are no known workarounds for this issue.(CVE-2022-31117)

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 operation leaks the full size of the serialized payload. This vulnerability is fixed in 5.12.1.(CVE-2026-44660)

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.(CVE-2026-54911)

Database specific

{
    "severity": "High"
}

References

Affected packages

openEuler:20.03-LTS-SP4 / python-ujson

Package

Name: python-ujson
Purl: pkg:rpm/openEuler/python-ujson&distro=openEuler-20.03-LTS-SP4

Affected ranges

Type: ECOSYSTEM
Events: Introduced

0Unknown introduced version / All previous versions are affected

Fixed

4.0.2-3.oe2003sp4

Ecosystem specific

{
    "src": [
        "python-ujson-4.0.2-3.oe2003sp4.src.rpm"
    ],
    "x86_64": [
        "python-ujson-debuginfo-4.0.2-3.oe2003sp4.x86_64.rpm",
        "python-ujson-debugsource-4.0.2-3.oe2003sp4.x86_64.rpm",
        "python-ujson-help-4.0.2-3.oe2003sp4.x86_64.rpm",
        "python3-ujson-4.0.2-3.oe2003sp4.x86_64.rpm"
    ],
    "aarch64": [
        "python-ujson-debuginfo-4.0.2-3.oe2003sp4.aarch64.rpm",
        "python-ujson-debugsource-4.0.2-3.oe2003sp4.aarch64.rpm",
        "python-ujson-help-4.0.2-3.oe2003sp4.aarch64.rpm",
        "python3-ujson-4.0.2-3.oe2003sp4.aarch64.rpm"
    ]
}

Database specific

source

"https://repo.openeuler.org/security/data/osv/OESA-2026-3606.json"