CVE-2026-32874UltraJSON is a fast JSON encoder and decoder written in pure C with bindings for Python 3.7+.
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No exploitation reported and no EPSS estimate yet.
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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
- 7.5 HIGH (v3.1, NVD)CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- Weakness (CWE)
- CWE-401, CWE-772
- Known exploited
- Not in CISA's KEV catalog
- EPSS (exploitation in the next 30 days)
- Not loaded for this CVE
- Assigned by
- Not given
- NVD analysis
- Modified
- Record last updated
- Jul 15, 2026
- First seen by InfoSec Signals
- Oct 9, 2026
Affected products
ultrajson_project ultrajson ultrajson_project:ultrajson | from 5.4.0 before 5.12.0 | NVD |
References
- https://github.com/ultrajson/ultrajson/commit/4baeb950df780092bd3c89fc702a868e99a3a1d2patch
- https://github.com/ultrajson/ultrajson/releases/tag/5.12.0product, release-notes
- https://github.com/ultrajson/ultrajson/security/advisories/GHSA-wgvc-ghv9-3pmmvendor-advisory
- https://access.redhat.com/security/cve/CVE-2026-32874
- https://bugzilla.redhat.com/show_bug.cgi?id=2449411
- https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-32874.json
The CVE record on cve.org NVD's entry
The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.