CVE-2026-44660UltraJSON is a fast JSON encoder and decoder written in pure C with bindings for Python 3.7+.
Updated under an hour ago ()
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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+. Prior to 5.12.1, when ujson.dump() writes to a file-like object and the write operation raises an exception, the serialized JSON string object is not decremented, leaking memory. Each failed write operation leaks the full size of the serialized payload. This vulnerability is fixed in 5.12.1.
- 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
- 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
- Analyzed
- Record last updated
- Jun 17, 2026
- First seen by InfoSec Signals
- Oct 9, 2026
Affected products
ultrajson_project ultrajson ultrajson_project:ultrajson | before 5.12.1 | NVD |
References
- https://github.com/ultrajson/ultrajson/commit/82af1d0ac01d09aa40c887b460d44b9d9f4bccd9patch
- https://github.com/ultrajson/ultrajson/releases/tag/5.12.1product, release-notes
- https://github.com/ultrajson/ultrajson/security/advisories/GHSA-c38f-wx89-p2xgexploit, mitigation, patch, vendor-advisory
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.