CVE-2021-43848

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This vulnerability exists in h2o server with HTTP/3 support, between commit 93af138 and d1f0f65. None of the released versions of h2o are affected by this vulnerability. There are no known workarounds. 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Also, if there is an HTTP endpoint that reflects the traffic sent from the client, an attacker can use that reflector to obtain internal state of h2o. This internal state includes traffic of other connections in unencrypted form and TLS session tickets. This vulnerability exists in h2o server with HTTP/3 support, between commit 93af138 and d1f0f65. None of the released versions of h2o are affected by this vulnerability. There are no known workarounds. Users of unreleased versions of h2o using HTTP/3 are advised to upgrade immediately."}, {"lang": "es", "value": "h2o es un servidor http de c\u00f3digo abierto. En el c\u00f3digo anterior al commit \"8c0eca3\" h2o puede intentar acceder a memoria no inicializada. Cuando son recibidas tramas QUIC en determinado orden, la implementaci\u00f3n del lado del servidor HTTP/3 de h2o puede equivocarse al tratar la memoria no inicializada como tramas HTTP/3 que se han recibido. Cuando h2o es usado como un proxy inverso, un atacante puede abusar de esta vulnerabilidad para enviar el estado interno de h2o a servidores backend controlados por el atacante o por terceros. Adem\u00e1s, si se presenta un endpoint HTTP que refleja el tr\u00e1fico enviado desde el cliente, un atacante puede usar ese reflector para obtener el estado interno de h2o. Este estado interno incluye el tr\u00e1fico de otras conexiones en forma no encriptada y los tickets de sesi\u00f3n TLS. Esta vulnerabilidad se presenta en el servidor h2o con soporte HTTP/3, entre el commit 93af138 y el d1f0f65. Ninguna de las versiones liberadas de h2o est\u00e1 afectada por esta vulnerabilidad. No se conocen medidas de mitigaci\u00f3n adicionales. Se recomienda a usuarios de versiones no liberadas de h2o que usen HTTP/3 que actualicen inmediatamente"}], "id": "CVE-2021-43848", "lastModified": "2026-06-17T04:11:33.900", "metrics": {"cvssMetricV2": [{"acInsufInfo": false, "baseSeverity": "MEDIUM", "cvssData": {"accessComplexity": "MEDIUM", "accessVector": "NETWORK", "authentication": "NONE", "availabilityImpact": "NONE", "baseScore": 4.3, "confidentialityImpact": "PARTIAL", "integrityImpact": "NONE", "vectorString": "AV:N/AC:M/Au:N/C:P/I:N/A:N", "version": "2.0"}, "exploitabilityScore": 8.6, "impactScore": 2.9, "obtainAllPrivilege": false, "obtainOtherPrivilege": false, "obtainUserPrivilege": false, "source": "nvd@nist.gov", "type": "Primary", "userInteractionRequired": false}], "cvssMetricV31": [{"cvssData": {"attackComplexity": "HIGH", "attackVector": "NETWORK", "availabilityImpact": "HIGH", "baseScore": 7.4, "baseSeverity": "HIGH", "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:H", "version": "3.1"}, "exploitabilityScore": 2.2, "impactScore": 5.2, "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-2021-43848", "options": [{"exploitation": "none"}, {"automatable": "no"}, {"technicalImpact": "partial"}], "role": "CISA Coordinator", "timestamp": "2025-04-23T14:11:27.354319Z", "version": "2.0.3"}}]}, "published": "2022-02-01T13:15:09.717", "references": [{"source": "security-advisories@github.com", "tags": ["Patch", "Third Party Advisory"], "url": "https://github.com/h2o/h2o/commit/8c0eca3"}, {"source": "security-advisories@github.com", "tags": ["Third Party Advisory"], "url": "https://github.com/h2o/h2o/security/advisories/GHSA-f9xw-j925-m4m4"}, {"source": "af854a3a-2127-422b-91ae-364da2661108", "tags": ["Patch", "Third Party Advisory"], "url": "https://github.com/h2o/h2o/commit/8c0eca3"}, {"source": "af854a3a-2127-422b-91ae-364da2661108", "tags": ["Third Party Advisory"], "url": "https://github.com/h2o/h2o/security/advisories/GHSA-f9xw-j925-m4m4"}], "sourceIdentifier": "security-advisories@github.com", "vulnStatus": "Modified", "weaknesses": [{"description": [{"lang": "en", "value": "CWE-908"}], "source": "security-advisories@github.com", "type": "Secondary"}]}

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