CVE-2026-32874

NameCVE-2026-32874
DescriptionUltraJSON 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.
SourceCVE (at NVD; CERT, ENISA, LWN, oss-sec, fulldisc, Debian ELTS, Red Hat, Ubuntu, Gentoo, SUSE bugzilla/CVE, GitHub advisories/code/issues, web search, more)

Vulnerable and fixed packages

The table below lists information on source packages.

Source PackageReleaseVersionStatus
ujson (PTS)bullseye4.0.2-1vulnerable
bookworm5.7.0-1vulnerable
trixie5.10.0-1vulnerable
forky, sid5.11.0-3vulnerable

The information below is based on the following data on fixed versions.

PackageTypeReleaseFixed VersionUrgencyOriginDebian Bugs
ujsonsource(unstable)(unfixed)

Notes

https://github.com/ultrajson/ultrajson/security/advisories/GHSA-wgvc-ghv9-3pmm
Fixed by: https://github.com/ultrajson/ultrajson/commit/4baeb950df780092bd3c89fc702a868e99a3a1d2 (5.12.0)

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