{"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":"2026-08-03T13:23:06.454Z"},"containers":{"cna":{"providerMetadata":{"orgId":"91579145-5d7b-4cc5-b925-a0262ff19630","shortName":"bcorg","dateUpdated":"2026-08-03T05:06:18.285Z"},"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%E2%80%902026%E2%80%9059638","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"}},"adp":[{"metrics":[{"other":{"type":"ssvc","content":{"timestamp":"2026-08-03T13:22:54.412148Z","id":"CVE-2026-59638","options":[{"Exploitation":"none"},{"Automatable":"yes"},{"Technical Impact":"total"}],"role":"CISA Coordinator","version":"2.0.3"}}}],"title":"CISA ADP Vulnrichment","providerMetadata":{"orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","shortName":"CISA-ADP","dateUpdated":"2026-08-03T13:23:06.454Z"}}]}}