fast-xml-parser has an entity encoding bypass via regex injection in DOCTYPE entity names

MITRE NVD CVE.ORG JSON API Print: PDF PDF

Summary

CVECVE-2026-25896
StatePUBLISHED
AssignerGitHub_M
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-02-20 21:19:27 UTC
Updated2026-06-30 03:17:45 UTC
Descriptionfast-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.

Risk And Classification

Primary CVSS: v3.1 7.1 HIGH from ADP

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

Problem Types: CWE-185 | CWE-79 | CWE-185 CWE-185: Incorrect Regular Expression | CWE-79 Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')

VersionSourceTypeScoreSeverityVector
3.1ADPCVSS7.1HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:L
3.1[email protected]Secondary9.3CRITICALCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:H/A:N
3.10b0ca135-0b70-47e7-9f44-1890c2a1c46cSecondary7.1HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:L
3.1CNADECLARED9.3CRITICALCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:H/A:N

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
Required
Scope
Changed
Confidentiality
Low
Integrity
Low
Availability
Low

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

NVD Known Affected Configurations (CPE 2.3)

TypeVendorProductVersionUpdateEditionLanguage
Application Naturalintelligence Fast-xml-parser All All All All

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA NaturalIntelligence Fast-xml-parser affected >= 5.0.0, < 5.3.5 Not specified
CNA NaturalIntelligence Fast-xml-parser affected >= 4.1.3, < 4.5.4 Not specified
ADP Red Hat Red Hat Advanced Cluster Security For Kubernetes 4.8 Not specified Not specified
ADP Red Hat Red Hat Advanced Cluster Security For Kubernetes 4.9 Not specified Not specified
ADP Red Hat Red Hat Developer Hub 1.8 Not specified Not specified
ADP Red Hat Red Hat Developer Hub 1.9 Not specified Not specified
ADP Red Hat Migration Toolkit For Applications 8 Not specified Not specified
ADP Red Hat Red Hat Openshift Data Foundation 4 Not specified Not specified
ADP Red Hat Red Hat OpenShift GitOps Not specified Not specified
ADP Red Hat Red Hat OpenShift Virtualization 4 Not specified Not specified
ADP Red Hat Red Hat Satellite 6 Not specified Not specified
ADP Red Hat Self-service Automation Portal 2 Not specified Not specified

References

ReferenceSourceLinkTags
github.com/NaturalIntelligence/fast-xml-parser/security/advisories/GHSA-... [email protected] github.com Exploit, Mitigation, Vendor Advisory
github.com/NaturalIntelligence/fast-xml-parser/commit/943ef0eb1b2d3284e7... [email protected] github.com Patch
github.com/NaturalIntelligence/fast-xml-parser/releases/tag/v5.3.5 [email protected] github.com Product, Release Notes
security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-25896.json 0b0ca135-0b70-47e7-9f44-1890c2a1c46c security.access.redhat.com
github.com/NaturalIntelligence/fast-xml-parser/commit/ddcd0acf26ddd682cb... [email protected] github.com Patch
access.redhat.com/errata/RHSA-2026:6802 0b0ca135-0b70-47e7-9f44-1890c2a1c46c access.redhat.com
access.redhat.com/security/cve/CVE-2026-25896 0b0ca135-0b70-47e7-9f44-1890c2a1c46c access.redhat.com
access.redhat.com/errata/RHSA-2026:6174 0b0ca135-0b70-47e7-9f44-1890c2a1c46c access.redhat.com
access.redhat.com/errata/RHSA-2026:7110 0b0ca135-0b70-47e7-9f44-1890c2a1c46c access.redhat.com
access.redhat.com/errata/RHSA-2026:7128 0b0ca135-0b70-47e7-9f44-1890c2a1c46c access.redhat.com
bugzilla.redhat.com/show_bug.cgi 0b0ca135-0b70-47e7-9f44-1890c2a1c46c bugzilla.redhat.com
CVE Program record CVE.ORG www.cve.org canonical
NVD vulnerability detail NVD nvd.nist.gov canonical, analysis

Additional Advisory Data

SourceTimeEvent
ADP2026-02-20T22:01:59.622ZReported to Red Hat.
ADP2026-02-20T20:57:48.074ZMade public.

Solutions

ADP: RHSA-2026:7110: Red Hat Advanced Cluster Security for Kubernetes 4.8

ADP: RHSA-2026:7128: Red Hat Advanced Cluster Security for Kubernetes 4.9

ADP: RHSA-2026:6174: Red Hat Developer Hub 1.8

ADP: RHSA-2026:6802: Red Hat Developer Hub 1.9

Workarounds

ADP: Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base or stability.

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