{"dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": {"cveId": "CVE-2026-59638", "assignerOrgId": "91579145-5d7b-4cc5-b925-a0262ff19630", "state": "PUBLISHED", "assignerShortName": "bcorg", "dateReserved": "2026-07-06T06:58:29.263Z", "datePublished": "2026-08-03T00:57:31.904Z", "dateUpdated": "2026-08-03T00:57:31.904Z"}, "containers": {"cna": {"providerMetadata": {"orgId": "91579145-5d7b-4cc5-b925-a0262ff19630", "shortName": "bcorg", "dateUpdated": "2026-08-03T00:57:31.904Z"}, "title": "JSSE hostname verifier CN-fallback enabled by default despite documented opt-in", "problemTypes": [{"descriptions": [{"lang": "en", "cweId": "CWE-297", "description": "CWE-297 Improper Validation of Certificate with Host Mismatch", "type": "CWE"}]}], "affected": [{"vendor": "Legion of the Bouncy Castle Inc.", "product": "BC-JAVA", "platforms": ["all"], "collectionURL": "https://www.bouncycastle.org/download/bouncy-castle-java/", "packageName": "bctls", "repo": "https://github.com/bcgit/bc-java", "packageURL": "pkg:maven/org.bouncycastle/bctls-jdk18on", "modules": ["tls"], "programFiles": ["HostnameUtil"], "versions": [{"status": "affected", "version": "1.61", "lessThan": "1.85", "versionType": "maven"}], "defaultStatus": "unaffected"}, {"vendor": "Legion of the Bouncy Castle Inc.", "product": "BC-LTS-JAVA", "platforms": ["all"], "collectionURL": "https://www.bouncycastle.org/download/bouncy-castle-java-lts/", "packageName": "bctls-lts8on", "repo": "https://github.com/bcgit/bc-lts-java", "packageURL": "pkg:maven/org.bouncycastle/bctls-lts8on", "modules": ["tls"], "programFiles": ["HostnameUtil"], "versions": [{"status": "affected", "version": "2.73.0", "lessThan": "2.73.12", "versionType": "maven"}], "defaultStatus": "unaffected"}, {"vendor": "Legion of the Bouncy Castle Inc.", "product": "BC-FJA", "platforms": ["all"], "collectionURL": "https://www.bouncycastle.org/download/bouncy-castle-java-fips/", "packageName": "bctls-fips", "packageURL": "pkg:maven/org.bouncycastle/bctls-fips", "versions": [{"status": "affected", "version": "1.0.7", "lessThan": "1.0.24", "versionType": "maven"}, {"status": "affected", "version": "2.0.0", "lessThan": "2.0.24", "versionType": "maven"}, {"status": "affected", "version": "2.1.0", "lessThan": "2.1.24", "versionType": "maven"}], "defaultStatus": "unaffected"}], "descriptions": [{"lang": "en", "value": "In Bouncy Castle for Java before 1.85, JSSE hostname verifier CN-fallback enabled by default despite documented opt-in. This issue also affects Bouncy Castle for Java LTS before 2.73.12, and Bouncy Castle for Java FIPS (BC-FJA) before bctls-fips 1.0.24 (1.0.X series), 2.0.24 (2.0.X series) and 2.1.24 (2.1.X series).", "supportingMedia": [{"type": "text/html", "base64": false, "value": "<p>In Bouncy Castle for Java before 1.85, JSSE hostname verifier CN-fallback enabled by default despite documented opt-in. This issue also affects Bouncy Castle for Java LTS before 2.73.12, and Bouncy Castle for Java FIPS (BC-FJA) before bctls-fips 1.0.24 (1.0.X series), 2.0.24 (2.0.X series) and 2.1.24 (2.1.X series).</p>"}]}], "references": [{"url": "https://github.com/bcgit/bc-java/wiki/CVE-2026-59638", "tags": ["vendor-advisory"]}, {"url": "https://github.com/bcgit/bc-java/commit/799bd15320a6310a447863638aa3df64acef829b", "tags": ["patch"]}, {"url": "https://github.com/bcgit/bc-java/commit/5ac55351cd1a8a7184d41c96a7ee87df0770240a", "tags": ["patch"]}], "metrics": [{"format": "CVSS", "scenarios": [{"lang": "en", "value": "GENERAL"}], "cvssV4_0": {"attackVector": "NETWORK", "attackComplexity": "LOW", "attackRequirements": "NONE", "privilegesRequired": "NONE", "userInteraction": "NONE", "vulnConfidentialityImpact": "HIGH", "subConfidentialityImpact": "NONE", "vulnIntegrityImpact": "HIGH", "subIntegrityImpact": "NONE", "vulnAvailabilityImpact": "NONE", "subAvailabilityImpact": "NONE", "exploitMaturity": "NOT_DEFINED", "Safety": "NOT_DEFINED", "Automatable": "NOT_DEFINED", "Recovery": "NOT_DEFINED", "valueDensity": "NOT_DEFINED", "vulnerabilityResponseEffort": "NOT_DEFINED", "providerUrgency": "AMBER", "version": "4.0", "baseSeverity": "CRITICAL", "baseScore": 9.3, "vectorString": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N/U:Amber"}}], "credits": [{"lang": "en", "value": "Alex Gaynor in collaboration with Claude and Anthropic Research", "type": "reporter"}], "source": {"discovery": "UNKNOWN"}, "x_generator": {"engine": "bc release-notes template"}}}}

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