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Description

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.

PUBLISHED Reserved 2026-05-07 | Published 2026-05-27 | Updated 2026-05-30 | Assigner GitHub_M




HIGH: 8.7CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N

Problem types

CWE-401: Missing Release of Memory after Effective Lifetime

Product status

< 5.12.1
affected

References

github.com/...rajson/security/advisories/GHSA-c38f-wx89-p2xg exploit

github.com/...rajson/security/advisories/GHSA-c38f-wx89-p2xg

github.com/...ommit/82af1d0ac01d09aa40c887b460d44b9d9f4bccd9

github.com/ultrajson/ultrajson/releases/tag/5.12.1

cve.org (CVE-2026-44660)

nvd.nist.gov (CVE-2026-44660)

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