CVE-2026-66046
Full vulnerability record from the local CVENow database.
Description
Expat through 2.8.3 contains a denial of service vulnerability caused by quadratic algorithmic complexity in the storeAtts() function in xmlparse.c, where processing N specified attributes with non-normalized values triggers an O(N^2) linear scan of elementType->defaultAtts to determine CDATA status. A remote unauthenticated attacker can supply a single well-formed XML document of a few megabytes to an application parsing untrusted XML to cause excessive CPU consumption, resulting in denial of service without requiring authentication, external entity resolution, or non-default parser options.
Severity
HIGH
CVSS score
8.7
(v4.0)
Vulnerability status
Analyzed
Source identifier
Published
2026-08-18 15:16:57
Last modified
2026-10-22 22:10:00.250000
View original CVE JSON
{
"id": "CVE-2026-66046",
"sourceIdentifier": "[email protected]",
"published": "2026-08-18T15:16:57.000",
"lastModified": "2026-10-22T22:10:00.250",
"vulnStatus": "Analyzed",
"cveTags": [],
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"value": "Expat through 2.8.3 contains a denial of service vulnerability caused by quadratic algorithmic complexity in the storeAtts() function in xmlparse.c, where processing N specified attributes with non-normalized values triggers an O(N^2) linear scan of elementType->defaultAtts to determine CDATA status. A remote unauthenticated attacker can supply a single well-formed XML document of a few megabytes to an application parsing untrusted XML to cause excessive CPU consumption, resulting in denial of service without requiring authentication, external entity resolution, or non-default parser options."
},
{
"lang": "es",
"value": "Expat hasta 2.8.3 contiene una vulnerabilidad de denegación de servicio causada por la complejidad algorítmica cuadrática en la función storeAtts() en xmlparse.c, donde el procesamiento de N atributos especificados con valores no normalizados desencadena un escaneo lineal O(N^2) de elementType -> defaultAtts para determinar el estado CDATA. Un atacante remoto no autenticado puede suministrar un único documento XML bien formado de unos pocos megabytes a una aplicación que analiza XML no confiable para causar un consumo excesivo de CPU, lo que resulta en denegación de servicio sin requerir autenticación, resolución de entidades externas u opciones de analizador no predeterminadas."
}
],
"affected": [
{
"source": "[email protected]",
"affectedData": [
{
"vendor": "libexpat project",
"product": "libexpat",
"defaultStatus": "affected",
"repo": "https://github.com/libexpat/libexpat",
"packageURL": "pkg:github/libexpat/libexpat",
"versions": [
{
"version": "0",
"lessThanOrEqual": "2.8.3",
"versionType": "semver",
"status": "affected"
}
]
}
]
}
],
"metrics": {
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"cvssData": {
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"vulnIntegrityImpact": "NONE",
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"subAvailabilityImpact": "NONE",
"exploitMaturity": "NOT_DEFINED",
"confidentialityRequirement": "NOT_DEFINED",
"integrityRequirement": "NOT_DEFINED",
"availabilityRequirement": "NOT_DEFINED",
"modifiedAttackVector": "NOT_DEFINED",
"modifiedAttackComplexity": "NOT_DEFINED",
"modifiedAttackRequirements": "NOT_DEFINED",
"modifiedPrivilegesRequired": "NOT_DEFINED",
"modifiedUserInteraction": "NOT_DEFINED",
"modifiedVulnConfidentialityImpact": "NOT_DEFINED",
"modifiedVulnIntegrityImpact": "NOT_DEFINED",
"modifiedVulnAvailabilityImpact": "NOT_DEFINED",
"modifiedSubConfidentialityImpact": "NOT_DEFINED",
"modifiedSubIntegrityImpact": "NOT_DEFINED",
"modifiedSubAvailabilityImpact": "NOT_DEFINED",
"Safety": "NOT_DEFINED",
"Automatable": "NOT_DEFINED",
"Recovery": "NOT_DEFINED",
"valueDensity": "NOT_DEFINED",
"vulnerabilityResponseEffort": "NOT_DEFINED",
"providerUrgency": "NOT_DEFINED"
}
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"cvssMetricV31": [
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"ssvcV203": [
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"id": "CVE-2026-66046",
"options": [
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}
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"role": "CISA Coordinator",
"version": "2.0.3"
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"weaknesses": [
{
"source": "[email protected]",
"type": "Secondary",
"description": [
{
"lang": "en",
"value": "CWE-407"
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"configurations": [
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"source": "[email protected]",
"tags": [
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{
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"source": "[email protected]",
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}