CVSS 4.0
8.7 highCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:NCVE-2026-44660
High (8.7) in ultrajson project ultrajson. EPSS 0.4% chance of exploitation in the next 30 days. Fixed in ujson 5.12.1.
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.
Severity
CVSS 3.1
7.5 highCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H- EPSS
- 0.4% chance of exploitation in the next 30 days; higher than 36% of CVEs (scores of 2026-10-31)
- CWE
- CWE-401
- Published
- Modified
- Record from
- the NVD, synced
Affected
- ultrajson_project:ultrajson
Packages (OSV)
| Advisory | Ecosystem | Package | Affected | Fixed in |
|---|---|---|---|---|
| GHSA-c38f-wx89-p2xg | PyPI | ujson | <5.12.1 | 5.12.1 |
| PYSEC-2026-2293 | PyPI | ujson | <5.12.1 | 5.12.1 |
References
- https://github.com/ultrajson/ultrajson/commit/82af1d0ac01d09aa40c887b460d44b9d9f4bccd9
- https://github.com/ultrajson/ultrajson/releases/tag/5.12.1
- https://github.com/ultrajson/ultrajson/security/advisories/GHSA-c38f-wx89-p2xg
- https://github.com/ultrajson/ultrajson/security/advisories/GHSA-c38f-wx89-p2xg