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Fencer Vulns
high 7.5

CVE-2022-31116 json

Incorrect handling of invalid surrogate pair characters in ujson

published 2022-07-05 4 y ago modified 2026-07-07 4 mo ago also GHSA-wpqr-jcpx-745r , PYSEC-2026-1057 , EUVD-2022-6438

cvss
7.5
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
2.5%
EPSS 2.5% chance of exploitation in 30 days, percentile 85%
public exploits
0
none known

Summary

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.

Patch / fix

  • pypi ujson 5.4.0
  • ultrajson_project ultrajson 5.4.0
  • ujson Debian 14, Debian 13, Debian 12 5.4.0-1

debian advisories DEBIAN-CVE-2022-31116

  • ujson Ubuntu Pro 16.04 LTS 1.33-1ubuntu0.1~esm2
  • ujson Ubuntu Pro 18.04 LTS 1.35-2ubuntu0.1~esm1
  • ujson Ubuntu Pro 22.04 LTS 5.1.0-1ubuntu0.1~esm1

ubuntu advisories UBUNTU-CVE-2022-31116

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • python-ujson openstack 16.2, openstack 16.1 2.0.3-3.el8ost
  • python3-ujson openstack 16.2, openstack 16.1 2.0.3-3.el8ost

red hat advisories RHSA-2022:8864RHSA-2022:8850

  • python-ujson SLE Module for Package Hub 15 SP4, SLE Module for Package Hub 15 SP3, SLE Module for Development Tools 15 SP4 +3 more 1.35-150100.3.5.1

suse advisories SUSE-SU-2022:2673-1

  • python-ujson openSUSE Tumbleweed 5.10.0-1.5

opensuse advisories openSUSE-SU-2025:15107-1

  • py3-ujson Alpine 3.24, Alpine 3.23, Alpine 3.22 +6 more 5.4.0-r0

alpine advisories ALPINE-CVE-2022-31116

Alpine secdb © Alpine Linux, from https://secdb.alpinelinux.org via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2022-31116 updated cvss 7.5

python-ujson: improper decoding of escaped surrogate characters may lead to string corruption, key confusion or value overwriting

  • Red Hat OpenStack Platform 13 (Queens) python-ujson
    affected: no fix planned “Out of support scope”
  • Red Hat OpenStack Platform 16.1 python-ujson 2.0.3-3.el8ost, python3-ujson 2.0.3-3.el8ost
    fixed: vendor fix RHSA-2022:8864
  • Red Hat OpenStack Platform 16.2 python-ujson 2.0.3-3.el8ost, python3-ujson 2.0.3-3.el8ost
    fixed: vendor fix RHSA-2022:8850

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
Proof of concept is public
Automatable
yes
Technical impact
partial
Assessed
18 mo ago

Exploit prediction

2.54% chance of exploitation in the next 30 days, higher than 85% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

  • github.com https://github.com/ultrajson/ultrajson/security/advisories/GHSA-wpqr-jcpx-745r referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
CNA 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
NVD 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
NVD 2.0 5.0 AV:N/AC:L/Au:N/C:N/I:N/A:P
GitHub 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
OSV 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Affected packages

ecosystem package affected fixed in
pypi ujson
<5.4.0
5.4.0

Affected products

  • ultrajson ultrajson

Classification

Weakness
  • CWE-670 Always-Incorrect Control Flow Implementation

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.