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Vulnerability record · CVE-2022-31116 · published 5 July 2022

CVE-2022-31116: Ultrajson project ultrajson vulnerability

UUltrajson Project · Ultrajson

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.

7.5 CVSS 3.1 High EPSS 2.5% · top 15.6% CWE-670 · CWE-670
7.5CVSS 3.1 base score, v2 5.0
2.5%EPSS exploitation probability, 30 days
NoNot in CISA KEV
2Affected product versions listed by NVD
8References, 2 tagged exploit
17 Jun 2026Last modified by NVD

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.

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

Affected products

2 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
https://github.com/ultrajson/ultrajson/commit/67ec07183342589d602e0fcf7bb1ff3e19272687 PatchThird Party Advisory
https://github.com/ultrajson/ultrajson/security/advisories/GHSA-wpqr-jcpx-745r ExploitThird Party Advisory
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/NAU5N4A7EUK2AMUCOLYDD5A
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/OPPU5FZP3LCTXYORFH7NHUM
https://github.com/ultrajson/ultrajson/commit/67ec07183342589d602e0fcf7bb1ff3e19272687 PatchThird Party Advisory
https://github.com/ultrajson/ultrajson/security/advisories/GHSA-wpqr-jcpx-745r ExploitThird Party Advisory
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/NAU5N4A7EUK2AMUCOLYDD5A
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/OPPU5FZP3LCTXYORFH7NHUM

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Source: NIST National Vulnerability Database (record CVE-2022-31116), CISA KEV, FIRST EPSS (scores of 2026-09-27). This page is refreshed as NVD updates the record.