CVE-2026-59638

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).

CVSS v3 6.5 MEDIUM

6.5^/10

CVSS v3 : MEDIUM

Vector :

Exploitability : 3.9 / Impact : 2.5

Attack Vector NETWORK

Attack Complexity LOW

Privileges Required NONE

User Interaction NONE

Confidentiality Impact LOW

Integrity Impact LOW

Availability Impact NONE

Scope UNCHANGED

References

Link	Resource
https://github.com/bcgit/bc-java/commit/5ac55351cd1a8a7184d41c96a7ee87df0770240a	Patch
https://github.com/bcgit/bc-java/commit/799bd15320a6310a447863638aa3df64acef829b	Patch
https://github.com/bcgit/bc-java/wiki/CVE%E2%80%902026%E2%80%9059638	Third Party Advisory

Configurations

Configuration 1 (hide)

OR	cpe:2.3:a:bouncycastle:bc-java::::::::
	cpe:2.3:a:bouncycastle:bctls-fips::::::::
	cpe:2.3:a:bouncycastle:bctls-fips::::::::
	cpe:2.3:a:bouncycastle:bctls-fips::::::::
	cpe:2.3:a:bouncycastle:bouncy_castle_for_java_lts::::::::

History

No history.

Information

Published : 2026-08-03 01:16

Updated : 2026-08-28 17:29

NVD link : CVE-2026-59638

Mitre link : CVE-2026-59638

CVE.ORG link : CVE-2026-59638

JSON object : View

Products Affected

bouncycastle

bouncy_castle_for_java_lts
bc-java
bctls-fips

CWE

CWE-297

Improper Validation of Certificate with Host Mismatch

{"id": "CVE-2026-59638", "cveTags": [], "metrics": {"ssvcV203": [{"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "ssvcData": {"id": "CVE-2026-59638", "role": "CISA Coordinator", "options": [{"exploitation": "none"}, {"automatable": "yes"}, {"technicalImpact": "total"}], "version": "2.0.3", "timestamp": "2026-08-03T13:22:54.412148Z"}}], "cvssMetricV31": [{"type": "Primary", "source": "nvd@nist.gov", "cvssData": {"scope": "UNCHANGED", "version": "3.1", "baseScore": 6.5, "attackVector": "NETWORK", "baseSeverity": "MEDIUM", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N", "integrityImpact": "LOW", "userInteraction": "NONE", "attackComplexity": "LOW", "availabilityImpact": "NONE", "privilegesRequired": "NONE", "confidentialityImpact": "LOW"}, "impactScore": 2.5, "exploitabilityScore": 3.9}], "cvssMetricV40": [{"type": "Secondary", "source": "91579145-5d7b-4cc5-b925-a0262ff19630", "cvssData": {"Safety": "NOT_DEFINED", "version": "4.0", "Recovery": "NOT_DEFINED", "baseScore": 9.3, "Automatable": "NOT_DEFINED", "attackVector": "NETWORK", "baseSeverity": "CRITICAL", "valueDensity": "NOT_DEFINED", "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/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:Amber", "exploitMaturity": "NOT_DEFINED", "providerUrgency": "AMBER", "userInteraction": "NONE", "attackComplexity": "LOW", "attackRequirements": "NONE", "privilegesRequired": "NONE", "subIntegrityImpact": "NONE", "vulnIntegrityImpact": "HIGH", "integrityRequirement": "NOT_DEFINED", "modifiedAttackVector": "NOT_DEFINED", "subAvailabilityImpact": "NONE", "vulnAvailabilityImpact": "NONE", "availabilityRequirement": "NOT_DEFINED", "modifiedUserInteraction": "NOT_DEFINED", "modifiedAttackComplexity": "NOT_DEFINED", "subConfidentialityImpact": "NONE", "vulnConfidentialityImpact": "HIGH", "confidentialityRequirement": "NOT_DEFINED", "modifiedAttackRequirements": "NOT_DEFINED", "modifiedPrivilegesRequired": "NOT_DEFINED", "modifiedSubIntegrityImpact": "NOT_DEFINED", "modifiedVulnIntegrityImpact": "NOT_DEFINED", "vulnerabilityResponseEffort": "NOT_DEFINED", "modifiedSubAvailabilityImpact": "NOT_DEFINED", "modifiedVulnAvailabilityImpact": "NOT_DEFINED", "modifiedSubConfidentialityImpact": "NOT_DEFINED", "modifiedVulnConfidentialityImpact": "NOT_DEFINED"}}]}, "affected": [{"source": "91579145-5d7b-4cc5-b925-a0262ff19630", "affectedData": [{"repo": "https://github.com/bcgit/bc-java", "vendor": "Legion of the Bouncy Castle Inc.", "modules": ["tls"], "product": "BC-JAVA", "versions": [{"status": "affected", "version": "1.61", "lessThan": "1.85", "versionType": "maven"}], "platforms": ["all"], "packageURL": "pkg:maven/org.bouncycastle/bctls-jdk18on", "packageName": "bctls", "programFiles": ["HostnameUtil"], "collectionURL": "https://www.bouncycastle.org/download/bouncy-castle-java/", "defaultStatus": "unaffected"}, {"repo": "https://github.com/bcgit/bc-lts-java", "vendor": "Legion of the Bouncy Castle Inc.", "modules": ["tls"], "product": "BC-LTS-JAVA", "versions": [{"status": "affected", "version": "2.73.0", "lessThan": "2.73.12", "versionType": "maven"}], "platforms": ["all"], "packageURL": "pkg:maven/org.bouncycastle/bctls-lts8on", "packageName": "bctls-lts8on", "programFiles": ["HostnameUtil"], "collectionURL": "https://www.bouncycastle.org/download/bouncy-castle-java-lts/", "defaultStatus": "unaffected"}, {"vendor": "Legion of the Bouncy Castle Inc.", "product": "BC-FJA", "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"}], "platforms": ["all"], "packageURL": "pkg:maven/org.bouncycastle/bctls-fips", "packageName": "bctls-fips", "collectionURL": "https://www.bouncycastle.org/download/bouncy-castle-java-fips/", "defaultStatus": "unaffected"}]}], "published": "2026-08-03T01:16:43.543", "references": [{"url": "https://github.com/bcgit/bc-java/commit/5ac55351cd1a8a7184d41c96a7ee87df0770240a", "tags": ["Patch"], "source": "91579145-5d7b-4cc5-b925-a0262ff19630"}, {"url": "https://github.com/bcgit/bc-java/commit/799bd15320a6310a447863638aa3df64acef829b", "tags": ["Patch"], "source": "91579145-5d7b-4cc5-b925-a0262ff19630"}, {"url": "https://github.com/bcgit/bc-java/wiki/CVE%E2%80%902026%E2%80%9059638", "tags": ["Third Party Advisory"], "source": "91579145-5d7b-4cc5-b925-a0262ff19630"}], "vulnStatus": "Analyzed", "weaknesses": [{"type": "Secondary", "source": "91579145-5d7b-4cc5-b925-a0262ff19630", "description": [{"lang": "en", "value": "CWE-297"}]}], "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)."}], "lastModified": "2026-08-28T17:29:17.083", "configurations": [{"nodes": [{"negate": false, "cpeMatch": [{"criteria": "cpe:2.3:a:bouncycastle:bc-java:*:*:*:*:*:*:*:*", "vulnerable": true, "matchCriteriaId": "FA6A5663-2E62-44AA-8A64-A3CB0DC8813B", "versionEndExcluding": "1.85"}, {"criteria": "cpe:2.3:a:bouncycastle:bctls-fips:*:*:*:*:*:*:*:*", "vulnerable": true, "matchCriteriaId": "08420234-16EB-4911-B907-6354B4241167", "versionEndExcluding": "1.0.24", "versionStartIncluding": "1.0.0"}, {"criteria": "cpe:2.3:a:bouncycastle:bctls-fips:*:*:*:*:*:*:*:*", "vulnerable": true, "matchCriteriaId": "E59C75F1-DB26-4688-A772-817285432027", "versionEndExcluding": "2.0.24", "versionStartIncluding": "2.0.19"}, {"criteria": "cpe:2.3:a:bouncycastle:bctls-fips:*:*:*:*:*:*:*:*", "vulnerable": true, "matchCriteriaId": "03E93498-95D0-453F-83A9-07E2CAEFEA08", "versionEndExcluding": "2.1.24", "versionStartIncluding": "2.1.20"}, {"criteria": "cpe:2.3:a:bouncycastle:bouncy_castle_for_java_lts:*:*:*:*:*:*:*:*", "vulnerable": true, "matchCriteriaId": "F5ED4F42-08FF-4642-815D-1ED0C82FDBD2", "versionEndIncluding": "2.73.11"}], "operator": "OR"}]}], "sourceIdentifier": "91579145-5d7b-4cc5-b925-a0262ff19630"}