CVE-2026-44660
UltraJSON: Memory Leak in ujson.dump() on Write Failure
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.
INFO
Published Date :
May 27, 2026, 9:16 p.m.
Last Modified :
June 2, 2026, 6 p.m.
Remotely Exploit :
Yes !
Source :
[email protected]
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS 3.1 | HIGH | [email protected] | ||||
| CVSS 4.0 | HIGH | [email protected] |
Solution
- Update UltraJSON to version 5.12.1 or later.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2026-44660.
| URL | Resource |
|---|---|
| https://github.com/ultrajson/ultrajson/commit/82af1d0ac01d09aa40c887b460d44b9d9f4bccd9 | Patch |
| https://github.com/ultrajson/ultrajson/releases/tag/5.12.1 | Product Release Notes |
| https://github.com/ultrajson/ultrajson/security/advisories/GHSA-c38f-wx89-p2xg | Exploit Mitigation Patch Vendor Advisory |
| https://github.com/ultrajson/ultrajson/security/advisories/GHSA-c38f-wx89-p2xg | Exploit Mitigation Patch Vendor Advisory |
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-44660 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2026-44660
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2026-44660 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2026-44660 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
-
Initial Analysis by [email protected]
Jun. 02, 2026
Action Type Old Value New Value Added CVSS V3.1 AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H Added CPE Configuration OR *cpe:2.3:a:ultrajson_project:ultrajson:*:*:*:*:*:python:*:* versions up to (excluding) 5.12.1 Added Reference Type GitHub, Inc.: https://github.com/ultrajson/ultrajson/commit/82af1d0ac01d09aa40c887b460d44b9d9f4bccd9 Types: Patch Added Reference Type GitHub, Inc.: https://github.com/ultrajson/ultrajson/releases/tag/5.12.1 Types: Product, Release Notes Added Reference Type CISA-ADP: https://github.com/ultrajson/ultrajson/security/advisories/GHSA-c38f-wx89-p2xg Types: Exploit, Mitigation, Patch, Vendor Advisory Added Reference Type GitHub, Inc.: https://github.com/ultrajson/ultrajson/security/advisories/GHSA-c38f-wx89-p2xg Types: Exploit, Mitigation, Patch, Vendor Advisory -
CVE Modified by 134c704f-9b21-4f2e-91b3-4a467353bcc0
May. 30, 2026
Action Type Old Value New Value Added Reference https://github.com/ultrajson/ultrajson/security/advisories/GHSA-c38f-wx89-p2xg -
New CVE Received by [email protected]
May. 27, 2026
Action Type Old Value New Value Added 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. Added CVSS V4.0 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 Added CWE CWE-401 Added Reference https://github.com/ultrajson/ultrajson/commit/82af1d0ac01d09aa40c887b460d44b9d9f4bccd9 Added Reference https://github.com/ultrajson/ultrajson/releases/tag/5.12.1 Added Reference https://github.com/ultrajson/ultrajson/security/advisories/GHSA-c38f-wx89-p2xg