CVE-2026-26278— fast-xml-parser affected by DoS through entity expansion in DOCTYPE (no expansion limit)
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I. Basic Information for CVE-2026-26278
Vulnerability Information
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Vulnerability Title
fast-xml-parser affected by DoS through entity expansion in DOCTYPE (no expansion limit)
Source: NVD (National Vulnerability Database)
Vulnerability Description
fast-xml-parser allows users to validate XML, parse XML to JS object, or build XML from JS object without C/C++ based libraries and no callback. In versions 4.1.3 through 5.3.5, the XML parser can be forced to do an unlimited amount of entity expansion. With a very small XML input, it’s possible to make the parser spend seconds or even minutes processing a single request, effectively freezing the application. Version 5.3.6 fixes the issue. As a workaround, avoid using DOCTYPE parsing by `processEntities: false` option.
Source: NVD (National Vulnerability Database)
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Source: NVD (National Vulnerability Database)
Vulnerability Type
DTD中递归实体索引的不恰当限制(XML实体扩展)
Source: NVD (National Vulnerability Database)
Vulnerability Title
fast-xml-parser 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
fast-xml-parser是Natural Intelligence开源的一个库。用于在没有基于 C/C++ 的库和回调的情况下，快速验证 XML、解析 XML 和构建 XML。 fast-xml-parser 5.3.5及之前版本存在安全漏洞，该漏洞源于XML解析器可能被迫进行无限量的实体扩展，可能导致正则表达式拒绝服务。
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 |
|---|---|---|---|---|
| NaturalIntelligence | fast-xml-parser | >= 5.0.0, < 5.3.6 | - |
II. Public POCs for CVE-2026-26278
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|---|
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IV. Related Vulnerabilities
Same product: fast-xml-parser
- CVE-2026-41650
fast-xml-parser XMLBuilder: XML Comment and CDATA Injection - CVE-2026-33349
fast-xml-parser: Entity Expansion Limits Bypassed When Set t - CVE-2026-33036
fast-xml-parser affected by numeric entity expansion bypassi - CVE-2026-27942
fast-xml-parser has stack overflow in XMLBuilder with preser - CVE-2026-25896
fast-xml-parser has an entity encoding bypass via regex inje
Same vendor: NaturalIntelligence
- CVE-2026-41650
fast-xml-parser XMLBuilder: XML Comment and CDATA Injection - CVE-2026-33349
fast-xml-parser: Entity Expansion Limits Bypassed When Set t - CVE-2026-33036
fast-xml-parser affected by numeric entity expansion bypassi - CVE-2026-27942
fast-xml-parser has stack overflow in XMLBuilder with preser - CVE-2026-25896
fast-xml-parser has an entity encoding bypass via regex inje
Same weakness: CWE-776
- CVE-2026-40260
pypdf: Manipulated XMP metadata entity declarations can exha - CVE-2026-33036
fast-xml-parser affected by numeric entity expansion bypassi - CVE-2026-29074
SVGO: DoS through entity expansion in DOCTYPE (Billion Laugh - CVE-2026-27807
MarkUs: YAML alias (‘billion laughs’) DoS in config upload - CVE-2025-20369
Extensible Markup Language (XML) External Entity Injection (
V. Comments for CVE-2026-26278
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