Vulnerability Description
UltraJSON is a fast JSON encoder and decoder written in pure C with bindings for Python 3.7+. Versions 5.4.0 through 5.11.0 contain an accumulating memory leak in JSON parsing large (outside of the range [-2^63, 2^64 - 1]) integers. The leaked memory is a copy of the string form of the integer plus an additional NULL byte. The leak occurs irrespective of whether the integer parses successfully or is rejected due to having more than sys.get_int_max_str_digits() digits, meaning that any sized leak per malicious JSON can be achieved provided that there is no limit on the overall size of the payload. Any service that calls ujson.load()/ujson.loads()/ujson.decode() on untrusted inputs is affected and vulnerable to denial of service attacks. This issue has been fixed in version 5.12.0.
CVSS Score
HIGH
Affected Products
| Vendor | Product | Versions |
|---|---|---|
| Ultrajson Project | Ultrajson | >= 5.4.0, < 5.12.0 |
Related Weaknesses (CWE)
References
- https://github.com/ultrajson/ultrajson/commit/4baeb950df780092bd3c89fc702a868e99Patch
- https://github.com/ultrajson/ultrajson/releases/tag/5.12.0ProductRelease Notes
- https://github.com/ultrajson/ultrajson/security/advisories/GHSA-wgvc-ghv9-3pmmVendor Advisory
FAQ
What is CVE-2026-32874?
CVE-2026-32874 is a vulnerability with a CVSS score of 7.5 (HIGH). UltraJSON is a fast JSON encoder and decoder written in pure C with bindings for Python 3.7+. Versions 5.4.0 through 5.11.0 contain an accumulating memory leak in JSON parsing large (outside of the ra...
How severe is CVE-2026-32874?
CVE-2026-32874 has been rated HIGH with a CVSS base score of 7.5/10. Review the CVSS metrics above for detailed severity breakdown.
Is there a patch for CVE-2026-32874?
Check the references section above for vendor advisories and patch information. Affected products include: Ultrajson Project Ultrajson.