What’s Vulnerable › Vulnerabilities

CVE-2022-31117: Double free of buffer during string decoding in ujson

• Severity: medium (CVSS 5.9 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 1.9% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2022-07-05 · updated 2026-06-17
• Weakness: CWE-415

Description

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.

Affected products

• Fedoraproject Fedora: 35, 36
• ultrajson: before 5.4.0 — fixed in 5.4.0

How to fix

Upgrade to a fixed version: ultrajson 5.4.0. Check the vendor advisory for mitigations.

References

• https://github.com/ultrajson/ultrajson/commit/9c20de0f77b391093967e25d01fb48671104b15b
• https://github.com/ultrajson/ultrajson/security/advisories/GHSA-fm67-cv37-96ff
• https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/NAU5N4A7EUK2AMUCOLYDD5ARXAJYZBD2/
• https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/OPPU5FZP3LCTXYORFH7NHUMYA5X66IA7/
• https://github.com/ultrajson/ultrajson/commit/9c20de0f77b391093967e25d01fb48671104b15b
• https://github.com/ultrajson/ultrajson/security/advisories/GHSA-fm67-cv37-96ff
• https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/NAU5N4A7EUK2AMUCOLYDD5ARXAJYZBD2/
• https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/OPPU5FZP3LCTXYORFH7NHUMYA5X66IA7/

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