fast-xml-parser has an entity encoding bypass via regex injection in DOCTYPE entity names (NaturalIntelligence fast-xml-parser)
At a glance
- Source
- NVD
- EPSS
- EPSS 0.53 % · percentile 45 ()
- State
- PUBLISHED
- Published
- Updated
- Assigner
- GitHub_M
- NVD status
- Modified
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.
Weaknesses (CWE)
- CWE-185 — Incorrect Regular Expression
- CWE-79 — Improper Neutralization of Input During Web Page Generation
References
- https://github.com/NaturalIntelligence/fast-xml-parser/security/advisories/GHSA-m7jm-9gc2-mpf2
- https://github.com/NaturalIntelligence/fast-xml-parser/commit/943ef0eb1b2d3284e72dd74f44a042ee9f07026e
- https://github.com/NaturalIntelligence/fast-xml-parser/commit/ddcd0acf26ddd682cb0dc15a2bd6aa3b96bb1e69
- https://github.com/NaturalIntelligence/fast-xml-parser/releases/tag/v5.3.5
- https://access.redhat.com/security/cve/CVE-2026-25896
- https://bugzilla.redhat.com/show_bug.cgi?id=2441501
- https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-25896.json
- https://access.redhat.com/errata/RHSA-2026:7110
- https://access.redhat.com/errata/RHSA-2026:7128
- https://access.redhat.com/errata/RHSA-2026:6174
- https://access.redhat.com/errata/RHSA-2026:6802
- https://access.redhat.com/errata/RHSA-2026:41941
- https://access.redhat.com/errata/RHSA-2026:41944
- https://access.redhat.com/errata/RHSA-2026:40984
- https://access.redhat.com/errata/RHSA-2026:51349
Scores
| Version | Score | Vector | Scored by |
|---|---|---|---|
| CVSS 3.1 | CRITICAL 9.3 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:H/A:N | GitHub_M |
| CVSS 3.1 | HIGH 7.1 | CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:L | redhat-SADP |
| CVSS 3.1 | CRITICAL 9.3 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:H/A:N | NVD · security-advisories@github.com (Secondary) |
| CVSS 3.1 | HIGH 7.1 | CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:L | NVD · 0b0ca135-0b70-47e7-9f44-1890c2a1c46c (Secondary) |
Advisories
- GHSA-m7jm-9gc2-mpf2 — fast-xml-parser has an entity encoding bypass via regex injection in DOCTYPE entity names
European references
- ENISA EUVD · EUVD-2026-7529
- GCVE · GCVE-0-2026-25896
CERT-FR advisories
- CERTFR-2026-AVI-0667 — Multiples vulnérabilités dans les produits IBM · cert.ssi.gouv.fr
Affected configurations (NVD CPE)
cpe:2.3:a:naturalintelligence:fast-xml-parser:*:*:*:*:*:*:*:*≥ 4.1.3 < 5.3.5
Affected products
| Product | Versions |
|---|---|
| NaturalIntelligence · fast-xml-parser | affected >= 5.0.0, < 5.3.5 ; affected >= 4.1.3, < 4.5.4 |
Sources
| Source | Licence |
|---|---|
| CVE List (CVEProject cvelistV5) | CVE Program Terms of Use |
| EPSS (FIRST.org) | FIRST — attribution requested |
| ENISA EUVD | ENISA — reproduction authorised, source acknowledged |
| CERT-FR (ANSSI) | Licence Ouverte / Etalab 2.0 |
| NVD (NIST) via fkie-cad/nvd-json-data-feeds | Public domain — this product uses data from the NVD API but is not endorsed or certified by the NVD |