CVE-2026-25896
CRITICAL
GHSA-m7jm-9gc2-mpf2
CVSS Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:H/A:N
Lifecycle Timeline
4Tags
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. From 4.1.3to before 5.3.5, a dot (.) in a DOCTYPE entity name is treated as a regex wildcard during entity replacement, allowing an attacker to shadow built-in XML entities (<, >, &, ", ') with arbitrary values. This bypasses entity encoding and leads to XSS when parsed output is rendered. This vulnerability is fixed in 5.3.5.
Analysis
ReDoS in fast-xml-parser before fix via crafted XML. PoC and patch available.
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Remediation
Within 24 hours: Inventory all applications and dependencies using Fast-Xml-Parser and identify affected systems in production and development environments. Within 7 days: Apply vendor patch to upgrade Fast-Xml-Parser to version 5.3.6 or later across all systems; test patches in staging environment before production deployment. …
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External POC / Exploit Code
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