CVE-2026-33308

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{"affected": [{"affectedData": [{"product": "mod_gnutls", "vendor": "airtower-luna", "versions": [{"status": "affected", "version": "< 0.13.0"}]}], "source": "security-advisories@github.com"}], "configurations": [{"nodes": [{"cpeMatch": [{"criteria": "cpe:2.3:a:mod_gnutls_project:mod_gnutls:*:*:*:*:*:*:*:*", "matchCriteriaId": "E476F8C2-BB73-4776-A192-67E20C9CE6EC", "versionEndExcluding": "0.13.0", "vulnerable": true}], "negate": false, "operator": "OR"}]}], "cveTags": [], "descriptions": [{"lang": "en", "value": "Mod_gnutls is a TLS module for Apache HTTPD based on GnuTLS. Prior to version 0.13.0, code for client certificate verification did not check the key purpose as set in the Extended Key Usage extension. An attacker with access to the private key for a valid certificate issued by a CA trusted for TLS client authentication but designated for a different purpose could have used that certificate to improperly access resources requiring TLS client authentication. Server configurations that do not use client certificates (`GnuTLSClientVerify ignore`, the default) are not affected. The problem has been fixed in version 0.13.0 by rewriting certificate verification to use `gnutls_certificate_verify_peers()`, and requiring key purpose id-kp-clientAuth (also known as `tls_www_client` in GnuTLS) by default if the Extended Key Usage extension is present. The new `GnuTLSClientKeyPurpose` option allows overriding the expected key purpose if needed (please see the manual for details). Behavior for certificates without an Extended Key Usage extension is unchanged. If dedicated (sub-)CAs are used for issuing TLS client certificates only (not for any other purposes) the issue has no practical impact."}, {"lang": "es", "value": "Mod_gnutls es un m\u00f3dulo TLS para Apache HTTPD basado en GnuTLS. Antes de la versi\u00f3n 0.13.0, el c\u00f3digo para la verificaci\u00f3n de certificados de cliente no verificaba el prop\u00f3sito de la clave tal como se establece en la extensi\u00f3n de Uso Extendido de Clave. Un atacante con acceso a la clave privada de un certificado v\u00e1lido emitido por una CA de confianza para la autenticaci\u00f3n de cliente TLS pero designado para un prop\u00f3sito diferente podr\u00eda haber utilizado ese certificado para acceder indebidamente a recursos que requieren autenticaci\u00f3n de cliente TLS. Las configuraciones de servidor que no utilizan certificados de cliente ('GnuTLSClientVerify ignore', el valor predeterminado) no se ven afectadas. El problema se ha solucionado en la versi\u00f3n 0.13.0 reescribiendo la verificaci\u00f3n de certificados para usar 'gnutls_certificate_verify_peers()' y requiriendo el prop\u00f3sito de clave id-kp-clientAuth (tambi\u00e9n conocido como 'tls_www_client' en GnuTLS) por defecto si la extensi\u00f3n de Uso Extendido de Clave est\u00e1 presente. La nueva opci\u00f3n 'GnuTLSClientKeyPurpose' permite anular el prop\u00f3sito de clave esperado si es necesario (consulte el manual para m\u00e1s detalles). El comportamiento para certificados sin una extensi\u00f3n de Uso Extendido de Clave no ha cambiado. Si se utilizan CA (o sub-CA) dedicadas solo para emitir certificados de cliente TLS (no para ning\u00fan otro prop\u00f3sito), el problema no tiene impacto pr\u00e1ctico."}], "id": "CVE-2026-33308", "lastModified": "2026-06-17T10:37:17.780", "metrics": {"cvssMetricV31": [{"cvssData": {"attackComplexity": "HIGH", "attackVector": "NETWORK", "availabilityImpact": "NONE", "baseScore": 6.8, "baseSeverity": "MEDIUM", "confidentialityImpact": "HIGH", "integrityImpact": "NONE", "privilegesRequired": "NONE", "scope": "CHANGED", "userInteraction": "NONE", "vectorString": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:N/A:N", "version": "3.1"}, "exploitabilityScore": 2.2, "impactScore": 4.0, "source": "security-advisories@github.com", "type": "Secondary"}, {"cvssData": {"attackComplexity": "HIGH", "attackVector": "NETWORK", "availabilityImpact": "NONE", "baseScore": 5.9, "baseSeverity": "MEDIUM", "confidentialityImpact": "HIGH", "integrityImpact": "NONE", "privilegesRequired": "NONE", "scope": "UNCHANGED", "userInteraction": "NONE", "vectorString": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N", "version": "3.1"}, "exploitabilityScore": 2.2, "impactScore": 3.6, "source": "nvd@nist.gov", "type": "Primary"}], "ssvcV203": [{"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "ssvcData": {"id": "CVE-2026-33308", "options": [{"exploitation": "none"}, {"automatable": "no"}, {"technicalImpact": "partial"}], "role": "CISA Coordinator", "timestamp": "2026-03-24T13:33:54.255619Z", "version": "2.0.3"}}]}, "published": "2026-03-24T03:16:06.080", "references": [{"source": "security-advisories@github.com", "tags": ["Mitigation", "Vendor Advisory"], "url": "https://github.com/airtower-luna/mod_gnutls/security/advisories/GHSA-hm2g-m958-8qgh"}], "sourceIdentifier": "security-advisories@github.com", "vulnStatus": "Analyzed", "weaknesses": [{"description": [{"lang": "en", "value": "CWE-295"}], "source": "security-advisories@github.com", "type": "Secondary"}]}

{}

{"affected": [{"configurations": [{"platform": null, "status": "affected", "versions": {"scheme": "semver", "value": "[0,0.13.0)"}}], "enrichment": {"confidence": 100.0, "confidence_source": "cna", "scores": [{"score": 100.0, "source": "cna"}]}, "original": {"product": "mod_gnutls", "source": "cna", "vendor": "airtower-luna"}, "product": "mod_gnutls", "vendor": "airtower-luna"}], "analysis": {"en": {"generated_at": "2026-03-24T20:53:33.344080+00:00", "value": {"mitigation_remediation": ["Upgrade mod_gnutls to version 0.13.0 or later to restore proper key\u2011purpose checks and use gnutls_certificate_verify_peers() instead of custom code.", "If an upgrade cannot be performed immediately, configure the GnuTLSClientKeyPurpose option to explicitly require the clientAuth (id\u2011kp\u2011clientAuth) key purpose and verify that the CA chain used for client authentication does not include certificates issued for other purposes.", "Review server configurations to ensure client certificate verification is only enabled when necessary; disable GnuTLSClientVerify when client authentication is not required.", "Stay informed of updates from the mod_gnutls project and apply security patches as soon as they become available."], "summary": {"action": "Patch immediately", "impact": "TLS client authentication bypass"}, "threat_synthesis": {"affected_systems": "The vulnerability impacts all releases of the Airtower\u2011Luna mod_gnutls module prior to 0.13.0. Server configurations that do not enforce client certificate verification (e.g., GnuTLSClientVerify set to ignore, which is the default) are not affected. If a deployment uses dedicated CAs that issue only client authentication certificates, the flaw poses no practical risk.", "description_and_impact": "Prior to version 0.13.0, the mod_gnutls module for Apache HTTPD failed to validate the key purpose specified in the Extended Key Usage extension during client certificate verification. An attacker possessing the private key of a certificate issued by a CA trusted for TLS client authentication but intended for another purpose could present that certificate during a TLS handshake, causing the server to accept it and grant access to resources protected by client\u2011certificate verification. This results in an unauthorized bypass of authentication, potentially compromising confidentiality and integrity of data accessed through such resources.", "risk_and_exploitability": "The CVSS score of 6.8 indicates a medium severity vulnerability with potential for significant impact if client certificate verification is in use. The EPSS score is below 1%, suggesting limited exploitation activity to date, and the vulnerability is not listed in the CISA KEV catalog. Exploitation requires the attacker to control a certificate issued for an alternative purpose by a trusted CA, and the server to require client authentication. For organizations that rely on client certificates for access control, prompt remediation is advisable to mitigate the risk of unauthorized access."}}}}, "created": "2026-03-24T10:29:25.319727+00:00", "updated": "2026-03-25T20:40:30.815632+00:00", "vendors": ["airtower-luna", "airtower-luna$PRODUCT$mod_gnutls"]}