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CVE-2026-44660— UltraJSON: Memory Leak in ujson.dump() on Write Failure

Quick assessment

Affected
ultrajson ultrajson
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

UltraJSON是UltraJSON开源的一个超快的 JSON 编码器和解码器，用纯 C 语言编写，并绑定了 Python 3.7+。 UltraJSON 5.12.1之前版本存在安全漏洞，该漏洞源于ujson.dump()写入文件类对象时若写入操作引发异常，序列化的JSON字符串对象未递减，导致内存泄漏。

AI Predicted 5.5 Difficulty: Easy EPSS 0.42% · P36

Possible ATT&CK Techniques 1 AI

T1498 · Network Denial of Service

Affected Version Matrix 1

VendorProduct Version RangeStatus
ultrajson ultrajson < 5.12.1 affected
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I. Basic Information for CVE-2026-44660

Vulnerability Information
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Vulnerability Title
UltraJSON: Memory Leak in ujson.dump() on Write Failure
Source: CVE Program / CVE List V5
Vulnerability 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.
Source: CVE Program / CVE List V5
CVSS Information
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
Source: CVE Program / CVE List V5
Vulnerability Type
在移除最后引用时对内存的释放不恰当(内存泄露)
Source: CVE Program / CVE List V5
Vulnerability Title
UltraJSON 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
UltraJSON是UltraJSON开源的一个超快的 JSON 编码器和解码器，用纯 C 语言编写，并绑定了 Python 3.7+。 UltraJSON 5.12.1之前版本存在安全漏洞，该漏洞源于ujson.dump()写入文件类对象时若写入操作引发异常，序列化的JSON字符串对象未递减，导致内存泄漏。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
ultrajson ultrajson < 5.12.1 -

II. Public POCs for CVE-2026-44660

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III. Intelligence Information for CVE-2026-44660

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Patches & Fixes for CVE-2026-44660 (1)

Vendor Advisories for CVE-2026-44660 (1)

Vendor Pages for CVE-2026-44660 (1)

IV. Related Vulnerabilities

Same product: ultrajson
Same vendor: ultrajson
Same weakness: CWE-401

V. Comments for CVE-2026-44660

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