CVE-2026-44660

Name: CVE-2026-44660
Creator: NVD / NIST
Published: 2026-05-27T21:16:17.65+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

HIGHCVSS 8.7/10EPSS 0.42%

Last modified Jun 17, 2026

CVE-2026-44660 is a high-severity vulnerability rated 8.7/10 on the CVSS scale. 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. EPSS estimates a 0.42% chance of exploitation in the next 30 days.

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.

Metrics

CVSS 3.1

7.5/10

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

CVSS 4.0

8.7/10

CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

EPSS Probability

0.42%

33.7th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-401

Affected Software

Vendor	Product	Versions
Ultrajson Project	Ultrajson	< 5.12.1

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
https://github.com/ultrajson/ultrajson/security/advisories/GHSA-c38f-wx89-p2xgExploit, Mitigation, Patch, Vendor Advisory

Timeline

Published: May 27, 2026
Last Modified: Jun 17, 2026
Status: Analyzed

Frequently Asked Questions

What is CVE-2026-44660?

How severe is CVE-2026-44660?

CVE-2026-44660 has a CVSS score of 8.7/10 (HIGH severity). The EPSS model estimates a 0.42% probability of exploitation in the next 30 days.

How do I fix CVE-2026-44660?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2026-44660?

Run a free Strix scan to check your systems for this vulnerability.

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Source: NVD / NIST