fast-xml-parser affected by numeric entity expansion bypassing all entity expansion limits (incomplete fix for CVE-2026-26278)

fast-xml-parser allows users to process XML from JS object without C/C++ based libraries or callbacks. Versions 4.0.0-beta.3 through 5.5.5 contain a bypass vulnerability where numeric character references (&#NNN;, &#xHH;) and standard XML entities completely evade the entity expansion limits (e.g., maxTotalExpansions, maxExpandedLength) added to fix CVE-2026-26278, enabling XML entity expansion Denial of Service. The root cause is that replaceEntitiesValue() in OrderedObjParser.js only enforces expansion counting on DOCTYPE-defined entities while the lastEntities loop handling numeric/standard entities performs no counting at all. An attacker supplying 1M numeric entity references like A can force ~147MB of memory allocation and heavy CPU usage, potentially crashing the process—even when developers have configured strict limits. This issue has been fixed in version 5.5.6.

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

DTD中递归实体索引的不恰当限制(XML实体扩展)

fast-xml-parser 安全漏洞

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 4.0.0-beta.3版本至5.5.5版本存在安全漏洞，该漏洞源于数字字符引用和标准XML实体绕过实体扩展限制，可能导致XML实体扩展拒绝服务攻击。

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