{"dataType": "CVE_RECORD", "cveMetadata": {"state": "PUBLISHED", "cveId": "CVE-2023-51764", "assignerOrgId": "8254265b-2729-46b6-b9e3-3dfca2d5bfca", "assignerShortName": "mitre", "dateUpdated": "2025-11-04T22:05:26.900Z", "dateReserved": "2023-12-24T00:00:00.000Z", "datePublished": "2023-12-24T00:00:00.000Z"}, "containers": {"cna": {"providerMetadata": {"orgId": "8254265b-2729-46b6-b9e3-3dfca2d5bfca", "shortName": "mitre", "dateUpdated": "2024-06-10T18:07:59.991Z"}, "descriptions": [{"lang": "en", "value": "Postfix through 3.8.5 allows SMTP smuggling unless configured with smtpd_data_restrictions=reject_unauth_pipelining and smtpd_discard_ehlo_keywords=chunking (or certain other options that exist in recent versions). Remote attackers can use a published exploitation technique to inject e-mail messages with a spoofed MAIL FROM address, allowing bypass of an SPF protection mechanism. This occurs because Postfix supports <LF>.<CR><LF> but some other popular e-mail servers do not. 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Remote attackers can use a published exploitation technique to inject e-mail messages with a spoofed MAIL FROM address, allowing bypass of an SPF protection mechanism. This occurs because Postfix supports <LF>.<CR><LF> but some other popular e-mail servers do not. To prevent attack variants (by always disallowing <LF> without <CR>), a different solution is required, such as the smtpd_forbid_bare_newline=yes option with a Postfix minimum version of 3.5.23, 3.6.13, 3.7.9, 3.8.4, or 3.9."}, {"lang": "es", "value": "Postfix hasta 3.8.4 permite el contrabando SMTP a menos que se configure con smtpd_data_restrictions=reject_unauth_pipelining (u otras opciones que existen en versiones recientes). Los atacantes remotos pueden utilizar una t\u00e9cnica de explotaci\u00f3n publicada para inyectar mensajes de correo electr\u00f3nico que parecen originarse en el servidor Postfix, lo que permite omitir un mecanismo de protecci\u00f3n SPF. Esto ocurre porque Postfix admite . pero algunos otros servidores de correo electr\u00f3nico populares no lo hacen. Para evitar variantes de ataque (al no permitir siempre sin ), se requiere una soluci\u00f3n diferente: la opci\u00f3n smtpd_forbid_bare_newline=yes con una versi\u00f3n m\u00ednima de Postfix de 3.5.23, 3.6.13, 3.7.9, 3.8.4, o 3.9."}], "id": "CVE-2023-51764", "lastModified": "2025-11-04T22:15:56.210", "metrics": {"cvssMetricV31": [{"cvssData": {"attackComplexity": "LOW", "attackVector": "NETWORK", "availabilityImpact": "NONE", "baseScore": 5.3, "baseSeverity": "MEDIUM", "confidentialityImpact": "NONE", "integrityImpact": "LOW", "privilegesRequired": "NONE", "scope": "UNCHANGED", "userInteraction": "NONE", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N", "version": "3.1"}, "exploitabilityScore": 3.9, "impactScore": 1.4, "source": "nvd@nist.gov", "type": "Primary"}]}, "published": "2023-12-24T05:15:08.273", "references": [{"source": "cve@mitre.org", "tags": ["Mailing List", "Third Party Advisory"], "url": "http://www.openwall.com/lists/oss-security/2023/12/24/1"}, 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{"affected_release": [{"advisory": "RHSA-2024:9243", "cpe": "cpe:/a:redhat:enterprise_linux:9", "package": "postfix-2:3.5.25-1.el9", "product_name": "Red Hat Enterprise Linux 9", "release_date": "2024-11-12T00:00:00Z"}], "bugzilla": {"description": "postfix: SMTP smuggling vulnerability", "id": "2255563", "url": "https://bugzilla.redhat.com/show_bug.cgi?id=2255563"}, "csaw": false, "cvss3": {"cvss3_base_score": "5.3", "cvss3_scoring_vector": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N", "status": "verified"}, "cwe": "CWE-345->CWE-451", "details": ["Postfix through 3.8.5 allows SMTP smuggling unless configured with smtpd_data_restrictions=reject_unauth_pipelining and smtpd_discard_ehlo_keywords=chunking (or certain other options that exist in recent versions). Remote attackers can use a published exploitation technique to inject e-mail messages with a spoofed MAIL FROM address, allowing bypass of an SPF protection mechanism. This occurs because Postfix supports <LF>.<CR><LF> but some other popular e-mail servers do not. To prevent attack variants (by always disallowing <LF> without <CR>), a different solution is required, such as the smtpd_forbid_bare_newline=yes option with a Postfix minimum version of 3.5.23, 3.6.13, 3.7.9, 3.8.4, or 3.9.", "A flaw was found in some SMTP server configurations in Postfix. This flaw allows a remote attacker to break out email message data to \"smuggle\" SMTP commands and send spoofed emails that pass SPF checks.\nOut of the box, Postfix targets to accommodate older clients with faulty SMTP implementations due to which restrictions are not enforced in the default configuration. Appropriate mitigation strategies are mentioned in the appropriate section below."], "mitigation": {"lang": "en:us", "value": "This flaw can be PARTIALLY mitigated via the following options in the main.cf:\nsmtpd_data_restrictions = reject_unauth_pipelining\nsmtpd_discard_ehlo_keywords = chunking, silent-discard\nPlease note this only blocks the misuse of SMTP command pipelining, but does not address message pipelining nor malformed line endings. The only fix for these issues are via package updates."}, "name": "CVE-2023-51764", "package_state": [{"cpe": "cpe:/o:redhat:enterprise_linux:6", "fix_state": "Out of support scope", "package_name": "postfix", "product_name": "Red Hat Enterprise Linux 6"}, {"cpe": "cpe:/o:redhat:enterprise_linux:7", "fix_state": "Out of support scope", "package_name": "postfix", "product_name": "Red Hat Enterprise Linux 7"}, {"cpe": "cpe:/o:redhat:enterprise_linux:8", "fix_state": "Fix deferred", "package_name": "postfix", "product_name": "Red Hat Enterprise Linux 8"}], "public_date": "2023-12-18T00:00:00Z", "references": ["https://www.cve.org/CVERecord?id=CVE-2023-51764\nhttps://nvd.nist.gov/vuln/detail/CVE-2023-51764\nhttps://sec-consult.com/blog/detail/smtp-smuggling-spoofing-e-mails-worldwide/\nhttps://www.postfix.org/smtp-smuggling.html"], "statement": "The impact is considered Moderate likely due to certain conditions required for successful exploitation, such as specific server configurations.", "threat_severity": "Moderate"}

{}