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CVE Record

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

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.

CriticalCVSS 9.3Not KEV-listedUpdated
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Potential ATT&CK relevance

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cwe · low confidence lookup

CWE-185: Exact CWE lookup

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cwe · medium confidence lookup

CWE-79: User-session and phishing behavior lookup

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cve · low confidence lookup

CVE-2026-25896 mapping review

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Vulnerability profileCVE Program record
Severity
Critical
CVSS
9.3 (3.1)
Known Exploited
No
Published

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

Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

2CVSS vectors
5Timeline events
2ADP providers
16Source links

SSVC decision data

CISA-ADPCISA Coordinator
Timestamp
Version
2.0.3
Exploitation: pocAutomatable: yesTechnical Impact: partial

CVSS vector scores

2 official scores

We collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.

ScoreVersionSeverityVectorExploitImpactSource
9.3CVSS 3.1CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:H/A:N3.94.7GitHub_M
7.1CVSS 3.1HighCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:L2.83.7redhat-SADP

Vulnerability scoring details

Base CVSS 3.1 score

9.3Critical
CVSS 3.1 vector shape for CVE-2026-25896Attack VectorAttack ComplexityPrivileges RequiredUser InteractionScopeConfidentiality ImpactIntegrity ImpactAvailability Impact

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

Attack Vector
NetworkAdjacentLocalPhysical
Attack Complexity
LowHigh
Privileges Required
NoneLowHigh
User Interaction
NoneRequired
Scope
ChangedUnchanged
Confidentiality Impact
HighLowNone
Integrity Impact
HighLowNone
Availability Impact
HighLowNone

Vulnerability timeline

Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.

  1. CVE reservedCVE Program

    The CVE ID was reserved by the assigning CNA.

  2. ADP timelineredhat-SADP

    Made public.

  3. CVE publishedCVE Program

    The CVE record was published.

  4. ADP timelineredhat-SADP

    Reported to Red Hat.

  5. CVE updatedCVE Program

    The CVE record metadata indicates this as the latest update time.

ADP provider summaries

CISA-ADPCISA ADP Vulnrichment
other:ssvc
redhat-SADPfast-xml-parser: fast-xml-parser: Cross-Site Scripting (XSS) due to improper DOCTYPE entity handling
other:Red Hat severity ratingcvssV3_1
  • 2026-02-20T22:01:59.622Z: Reported to Red Hat.
  • 2026-02-20T20:57:48.074Z: Made public.

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
NaturalIntelligencefast-xml-parser>= 5.0.0, < 5.3.5, >= 4.1.3, < 4.5.4Listed
Weakness

CWE details

CWE-185CWE-79

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CWE-185 · source CWE mapping

Incorrect Regular Expression

Incorrect Regular Expression represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.

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CWE-79 · source CWE mapping

Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')

Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.

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