CVE-2026-25896

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.

• github.comhttps://github.com/NaturalIntelligence/fast-xml-parser/commit/943ef0eb1b2d3284e72dd74f44a042ee9f07026e
• github.comhttps://github.com/NaturalIntelligence/fast-xml-parser/commit/ddcd0acf26ddd682cb0dc15a2bd6aa3b96bb1e69
• github.comhttps://github.com/NaturalIntelligence/fast-xml-parser/releases/tag/v5.3.5
• github.comhttps://github.com/NaturalIntelligence/fast-xml-parser/security/advisories/GHSA-m7jm-9gc2-mpf2
• access.redhat.comhttps://access.redhat.com/errata/RHSA-2026:40984
• access.redhat.comhttps://access.redhat.com/errata/RHSA-2026:6174
• access.redhat.comhttps://access.redhat.com/errata/RHSA-2026:6802
• access.redhat.comhttps://access.redhat.com/errata/RHSA-2026:7110
• access.redhat.comhttps://access.redhat.com/errata/RHSA-2026:7128
• access.redhat.comhttps://access.redhat.com/security/cve/CVE-2026-25896
• bugzilla.redhat.comhttps://bugzilla.redhat.com/show_bug.cgi?id=2441501
• security.access.redhat.comhttps://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-25896.json