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Critical 9.3Published Feb 20, 2026

CVE-2026-25896fast-xml-parser has an entity encoding bypass via regex injection in DOCTYPE entity names

Updated under an hour ago ()

Does this affect you?

It affects NaturalIntelligence fast-xml-parser and 9 other products. Add what you run to find out whether that includes you.

No exploitation reported and no EPSS estimate yet.

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.

CVSS
9.3 CRITICAL (v3.1, CNA)CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:H/A:N
Weakness (CWE)
CWE-185, CWE-79
Known exploited
Not in CISA's KEV catalog
EPSS (exploitation in the next 30 days)
Not loaded for this CVE
Assigned by
GitHub_M
NVD analysis
Modified
Record last updated
Sep 10, 2026
First seen by InfoSec Signals
Oct 9, 2026

Affected products

Affected products
NaturalIntelligence fast-xml-parser
naturalintelligence:fast_xml_parser (from the name)
from 5.0.0, < 5.3.5; from 4.1.3, < 4.5.4
CNA record
Red Hat Red Hat Advanced Cluster Security 4.8
redhat:advanced_cluster_security
from 1775594119 not affected
CISA ADP
from 1774545605 not affected
CISA ADP
Red Hat Red Hat Openshift Data Foundation 4.18
redhat:openshift_data_foundation
from 1783676191 not affected
CISA ADP
from 1785922764 not affected
CISA ADP
Red Hat Migration Toolkit for Applications 8
redhat:migration_toolkit_applications
8
CISA ADP
Red Hat Red Hat OpenShift GitOps
redhat:openshift_gitops
1
CISA ADP
Red Hat Red Hat OpenShift Virtualization 4
redhat:container_native_virtualization
4
CISA ADP
2
CISA ADP
naturalintelligence fast-xml-parser
naturalintelligence:fast-xml-parser
from 4.1.3 before 5.3.5
NVD

References

References

The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.

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