CVE-2022-31116: 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 certai...

Description

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.

Metrics

CVSS 3.1

7.5/10

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

EPSS Probability

1.83%

76.1th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-670

Affected Software

Vendor	Product	Versions
Ultrajson Project	Ultrajson	< 5.4.0
Fedoraproject	Fedora	35
Fedoraproject	Fedora	36

References

Timeline

Published: Jul 5, 2022
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2022-31116?

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.

How severe is CVE-2022-31116?

CVE-2022-31116 has a CVSS score of 7.5/10 (HIGH severity). The EPSS model estimates a 1.83% probability of exploitation in the next 30 days.

How do I fix CVE-2022-31116?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.