CVE-2026-103602 (GCVE-0-2026-103602)
Vulnerability from cvelistv5 – Published: 2026-10-02 07:10 – Updated: 2026-10-02 07:10
VLAI
EPSS
VEX
Title
Name constraints bypass via trailing dot in rfc822Name, dNSName and URI hosts
Summary
Improper certificate validation in PkixNameConstraintValidator in Legion of the Bouncy Castle Inc. bc-csharp before 2.7.0 allows an attacker who controls, or can obtain certificates from, a name-constrained intermediate CA to have certificates accepted during PKIX certification path validation for email addresses, DNS names or URI hosts that lie within excluded subtrees applying to that CA, via an rfc822Name, dNSName or uniformResourceIdentifier name whose host ends with a dot, because names and constraints were compared without first removing the RFC 1034 root-label trailing dot, so a fully qualified host name did not match an excluded subtree for the same host written without the dot.
Severity
CWE
- CWE-295 - Improper Certificate Validation
Assigner
References
4 references
Impacted products
1 product
| Vendor | Product | Version | |
|---|---|---|---|
| Legion of the Bouncy Castle Inc. | bc-csharp |
Affected:
0 , < 2.7.0
(semver)
|
{
"containers": {
"cna": {
"affected": [
{
"collectionURL": "https://www.nuget.org/packages/BouncyCastle.Cryptography",
"defaultStatus": "unaffected",
"packageName": "BouncyCastle.Cryptography",
"product": "bc-csharp",
"programFiles": [
"crypto/src/pkix/PkixNameConstraintValidator.cs",
"crypto/src/pkix/NameConstraintUtilities.cs",
"crypto/src/pkix/NameConstraintEmail.cs",
"crypto/src/pkix/NameConstraintDns.cs",
"crypto/src/pkix/NameConstraintUri.cs"
],
"repo": "https://github.com/bcgit/bc-csharp",
"vendor": "Legion of the Bouncy Castle Inc.",
"versions": [
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"status": "affected",
"version": "0",
"versionType": "semver"
}
]
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"credits": [
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"type": "finder",
"value": "Discovered by Claude, Anthropic\u0027s AI assistant, and triaged by the Anthropic security team in collaboration with Anthropic Research."
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}
],
"value": "Improper certificate validation in PkixNameConstraintValidator in Legion of the Bouncy Castle Inc. bc-csharp before 2.7.0 allows an attacker who controls, or can obtain certificates from, a name-constrained intermediate CA to have certificates accepted during PKIX certification path validation for email addresses, DNS names or URI hosts that lie within excluded subtrees applying to that CA, via an rfc822Name, dNSName or uniformResourceIdentifier name whose host ends with a dot, because names and constraints were compared without first removing the RFC 1034 root-label trailing dot, so a fully qualified host name did not match an excluded subtree for the same host written without the dot."
}
],
"impacts": [
{
"descriptions": [
{
"lang": "en",
"value": "Integrity (bypass of excluded rfc822Name, dNSName and uniformResourceIdentifier name constraints during certification path validation: certificates naming hosts inside an excluded subtree are accepted)"
}
]
}
],
"metrics": [
{
"cvssV4_0": {
"Automatable": "NOT_DEFINED",
"Recovery": "NOT_DEFINED",
"Safety": "NOT_DEFINED",
"attackComplexity": "LOW",
"attackRequirements": "PRESENT",
"attackVector": "NETWORK",
"baseScore": 8.2,
"baseSeverity": "HIGH",
"exploitMaturity": "NOT_DEFINED",
"privilegesRequired": "NONE",
"providerUrgency": "NOT_DEFINED",
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"subConfidentialityImpact": "NONE",
"subIntegrityImpact": "NONE",
"userInteraction": "NONE",
"valueDensity": "NOT_DEFINED",
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"version": "4.0",
"vulnAvailabilityImpact": "NONE",
"vulnConfidentialityImpact": "NONE",
"vulnIntegrityImpact": "HIGH",
"vulnerabilityResponseEffort": "NOT_DEFINED"
},
"format": "CVSS",
"scenarios": [
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"lang": "en",
"value": "GENERAL"
}
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"problemTypes": [
{
"descriptions": [
{
"cweId": "CWE-295",
"description": "CWE-295 Improper Certificate Validation",
"lang": "en",
"type": "CWE"
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"providerMetadata": {
"dateUpdated": "2026-10-02T07:10:03.885Z",
"orgId": "91579145-5d7b-4cc5-b925-a0262ff19630",
"shortName": "bcorg"
},
"references": [
{
"tags": [
"vendor-advisory"
],
"url": "https://github.com/bcgit/bc-csharp/wiki/CVE-2026-103602"
},
{
"tags": [
"patch"
],
"url": "https://github.com/bcgit/bc-csharp/commit/f196a22bbf7765cc19b0c4f4645c74ea7ad35e09"
},
{
"tags": [
"patch"
],
"url": "https://github.com/bcgit/bc-csharp/commit/be276e057775a6a674a62e9d9a2583b229978f73"
},
{
"tags": [
"patch"
],
"url": "https://github.com/bcgit/bc-csharp/commit/75c3c576602886180ed92a63c89419e3bd63b392"
}
],
"source": {
"discovery": "EXTERNAL"
},
"title": "Name constraints bypass via trailing dot in rfc822Name, dNSName and URI hosts",
"x_antReportIds": [
"ANT-2026-DXGD77QP"
],
"x_generator": {
"engine": "Claude Opus 5.5"
}
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},
"cveMetadata": {
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"assignerShortName": "bcorg",
"cveId": "CVE-2026-103602",
"datePublished": "2026-10-02T07:10:03.885Z",
"dateReserved": "2026-09-30T23:01:10.053Z",
"dateUpdated": "2026-10-02T07:10:03.885Z",
"state": "PUBLISHED"
},
"dataType": "CVE_RECORD",
"dataVersion": "5.2",
"vulnerability-lookup:meta": {
"nvd": {
"cve": {
"affected": [
{
"affectedData": [
{
"collectionURL": "https://www.nuget.org/packages/BouncyCastle.Cryptography",
"defaultStatus": "unaffected",
"packageName": "BouncyCastle.Cryptography",
"product": "bc-csharp",
"programFiles": [
"crypto/src/pkix/PkixNameConstraintValidator.cs",
"crypto/src/pkix/NameConstraintUtilities.cs",
"crypto/src/pkix/NameConstraintEmail.cs",
"crypto/src/pkix/NameConstraintDns.cs",
"crypto/src/pkix/NameConstraintUri.cs"
],
"repo": "https://github.com/bcgit/bc-csharp",
"vendor": "Legion of the Bouncy Castle Inc.",
"versions": [
{
"lessThan": "2.7.0",
"status": "affected",
"version": "0",
"versionType": "semver"
}
]
}
],
"source": "91579145-5d7b-4cc5-b925-a0262ff19630"
}
],
"cveTags": [],
"descriptions": [
{
"lang": "en",
"value": "Improper certificate validation in PkixNameConstraintValidator in Legion of the Bouncy Castle Inc. bc-csharp before 2.7.0 allows an attacker who controls, or can obtain certificates from, a name-constrained intermediate CA to have certificates accepted during PKIX certification path validation for email addresses, DNS names or URI hosts that lie within excluded subtrees applying to that CA, via an rfc822Name, dNSName or uniformResourceIdentifier name whose host ends with a dot, because names and constraints were compared without first removing the RFC 1034 root-label trailing dot, so a fully qualified host name did not match an excluded subtree for the same host written without the dot."
}
],
"id": "CVE-2026-103602",
"lastModified": "2026-10-02T08:17:00.677",
"metrics": {
"cvssMetricV40": [
{
"cvssData": {
"Automatable": "NOT_DEFINED",
"Recovery": "NOT_DEFINED",
"Safety": "NOT_DEFINED",
"attackComplexity": "LOW",
"attackRequirements": "PRESENT",
"attackVector": "NETWORK",
"availabilityRequirement": "NOT_DEFINED",
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"confidentialityRequirement": "NOT_DEFINED",
"exploitMaturity": "NOT_DEFINED",
"integrityRequirement": "NOT_DEFINED",
"modifiedAttackComplexity": "NOT_DEFINED",
"modifiedAttackRequirements": "NOT_DEFINED",
"modifiedAttackVector": "NOT_DEFINED",
"modifiedPrivilegesRequired": "NOT_DEFINED",
"modifiedSubAvailabilityImpact": "NOT_DEFINED",
"modifiedSubConfidentialityImpact": "NOT_DEFINED",
"modifiedSubIntegrityImpact": "NOT_DEFINED",
"modifiedUserInteraction": "NOT_DEFINED",
"modifiedVulnAvailabilityImpact": "NOT_DEFINED",
"modifiedVulnConfidentialityImpact": "NOT_DEFINED",
"modifiedVulnIntegrityImpact": "NOT_DEFINED",
"privilegesRequired": "NONE",
"providerUrgency": "NOT_DEFINED",
"subAvailabilityImpact": "NONE",
"subConfidentialityImpact": "NONE",
"subIntegrityImpact": "NONE",
"userInteraction": "NONE",
"valueDensity": "NOT_DEFINED",
"vectorString": "CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X",
"version": "4.0",
"vulnAvailabilityImpact": "NONE",
"vulnConfidentialityImpact": "NONE",
"vulnIntegrityImpact": "HIGH",
"vulnerabilityResponseEffort": "NOT_DEFINED"
},
"source": "91579145-5d7b-4cc5-b925-a0262ff19630",
"type": "Secondary"
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]
},
"published": "2026-10-02T08:17:00.677",
"references": [
{
"source": "91579145-5d7b-4cc5-b925-a0262ff19630",
"url": "https://github.com/bcgit/bc-csharp/commit/75c3c576602886180ed92a63c89419e3bd63b392"
},
{
"source": "91579145-5d7b-4cc5-b925-a0262ff19630",
"url": "https://github.com/bcgit/bc-csharp/commit/be276e057775a6a674a62e9d9a2583b229978f73"
},
{
"source": "91579145-5d7b-4cc5-b925-a0262ff19630",
"url": "https://github.com/bcgit/bc-csharp/commit/f196a22bbf7765cc19b0c4f4645c74ea7ad35e09"
},
{
"source": "91579145-5d7b-4cc5-b925-a0262ff19630",
"url": "https://github.com/bcgit/bc-csharp/wiki/CVE-2026-103602"
}
],
"sourceIdentifier": "91579145-5d7b-4cc5-b925-a0262ff19630",
"vulnStatus": "Received",
"weaknesses": [
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"description": [
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"lang": "en",
"value": "CWE-295"
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],
"source": "91579145-5d7b-4cc5-b925-a0262ff19630",
"type": "Secondary"
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}
}
}
}
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Experimental. This forecast is provided for visualization only and may change without notice. Do not use it for operational decisions.
Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.
Sightings
| Author | Source | Type | Date | Other |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or observed by the user.
- Confirmed: The vulnerability has been validated from an analyst's perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
- Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
- Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
- Not confirmed: The user expressed doubt about the validity of the vulnerability.
- Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.
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The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the
vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base
model, served locally by ML-Gateway.
They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.
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Related by attack behaviour
Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.
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