Potential double free of buffer during string decoding
Impact
What kind of vulnerability is it? Who is impacted?
When an error occurs while reallocating the buffer for string decoding, the buffer gets freed twice.
Due to how UltraJSON uses the internal decoder, this double free is impossible to trigger from Python.
Patches
Has the problem been patched? What versions should users upgrade to?
Users should upgrade to UltraJSON 5.4.0.
Workarounds
Is there a way for users to fix or remediate the vulnerability without upgrading?
There is no workaround.
For more information
If you have any questions or comments about this advisory:
- Open an issue in UltraJSON
Affected software
Click a technology to see all vulnerabilities affecting it.
| Platform | Package | Vulnerable versions | Fixed in |
|---|---|---|---|
| Python (PyPI) | ujson | < 5.4.0 | 5.4.0 |
References
- https://github.com/ultrajson/ultrajson/security/advisories/GHSA-fm67-cv37-96ff
- https://nvd.nist.gov/vuln/detail/CVE-2022-31117
- https://github.com/ultrajson/ultrajson/commit/9c20de0f77b391093967e25d01fb48671104b15b
- https://github.com/ultrajson/ultrajson
- https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/NAU5N4A7EUK2AMUCOLYDD5ARXAJYZBD2
- https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/OPPU5FZP3LCTXYORFH7NHUMYA5X66IA7
- https://pypi.org/project/ujson
- https://github.com/advisories/GHSA-fm67-cv37-96ff
- CVSS vector
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H- Weakness (CWE)
CWE-415- Platform
- Python (PyPI)
- Package
ujson- Disclosed
- 05.07.2022
- Updated
- 11.10.2026 13:18
Sources and licenses
OSV / GitHub Advisory Database - PYSEC-2026-1056 - PyPA Advisory Database; CC BY 4.0
OSV / GitHub Advisory Database - GHSA-fm67-cv37-96ff - CC BY 4.0
Vulnerability history: ujson
All published vulnerabilities of this package (Python (PyPI)), newest first. Shows whether this is a one-off slip or a package that needs watching.
- Total entries
- 7
- First → latest
- 01.2022 06.2026
- Without a fix
- 0
- Exploited in attacks
- 0
Severity breakdown
- High 4
- Medium 3
Disclosures per year
- 2022: 3
- 2023: 0
- 2024: 0
- 2025: 0
- 2026: 4
-
Potential double free of buffer during string decoding this entry
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