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CVE-2023-51766 (GCVE-0-2023-51766)

Vulnerability from cvelistv5 – Published: 2023-12-24 00:00 – Updated: 2025-11-04 18:21
VLAI
Summary
Exim before 4.97.1 allows SMTP smuggling in certain PIPELINING/CHUNKING configurations. 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 Exim supports <LF>.<CR><LF> but some other popular e-mail servers do not.
Severity
5.3 (Medium)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
CWE
  • n/a
Assigner
References
Show details on NVD website
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    "nvd": "{\"cve\":{\"id\":\"CVE-2023-51766\",\"sourceIdentifier\":\"cve@mitre.org\",\"published\":\"2023-12-24T06:15:07.673\",\"lastModified\":\"2026-06-17T06:41:37.057\",\"vulnStatus\":\"Modified\",\"cveTags\":[],\"descriptions\":[{\"lang\":\"en\",\"value\":\"Exim before 4.97.1 allows SMTP smuggling in certain PIPELINING/CHUNKING configurations. 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 Exim supports \u003cLF\u003e.\u003cCR\u003e\u003cLF\u003e but some other popular e-mail servers do not.\"},{\"lang\":\"es\",\"value\":\"Exim hasta 4.97 permite el contrabando SMTP en ciertas configuraciones. 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 Exim, permitiendo omitir un mecanismo de protecci\u00f3n SPF. Esto ocurre porque Exim admite . pero algunos otros servidores de correo electr\u00f3nico populares no lo hacen.\"}],\"affected\":[{\"source\":\"cve@mitre.org\",\"affectedData\":[{\"vendor\":\"n/a\",\"product\":\"n/a\",\"versions\":[{\"version\":\"n/a\",\"status\":\"affected\"}]}]}],\"metrics\":{\"cvssMetricV31\":[{\"source\":\"nvd@nist.gov\",\"type\":\"Primary\",\"cvssData\":{\"version\":\"3.1\",\"vectorString\":\"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N\",\"baseScore\":5.3,\"baseSeverity\":\"MEDIUM\",\"attackVector\":\"NETWORK\",\"attackComplexity\":\"LOW\",\"privilegesRequired\":\"NONE\",\"userInteraction\":\"NONE\",\"scope\":\"UNCHANGED\",\"confidentialityImpact\":\"NONE\",\"integrityImpact\":\"LOW\",\"availabilityImpact\":\"NONE\"},\"exploitabilityScore\":3.9,\"impactScore\":1.4}]},\"weaknesses\":[{\"source\":\"nvd@nist.gov\",\"type\":\"Primary\",\"description\":[{\"lang\":\"en\",\"value\":\"CWE-345\"}]}],\"configurations\":[{\"nodes\":[{\"operator\":\"OR\",\"negate\":false,\"cpeMatch\":[{\"vulnerable\":true,\"criteria\":\"cpe:2.3:a:exim:exim:*:*:*:*:*:*:*:*\",\"versionEndExcluding\":\"4.97.1\",\"matchCriteriaId\":\"95F6F151-E57F-4DB2-9CCD-3336B887A07B\"}]}]},{\"nodes\":[{\"operator\":\"OR\",\"negate\":false,\"cpeMatch\":[{\"vulnerable\":true,\"criteria\":\"cpe:2.3:a:fedoraproject:extra_packages_for_enterprise_linux:7.0:*:*:*:*:*:*:*\",\"matchCriteriaId\":\"3D9C7598-4BB4-442A-86DF-EEDE041A4CC7\"},{\"vulnerable\":true,\"criteria\":\"cpe:2.3:a:fedoraproject:extra_packages_for_enterprise_linux:8.0:*:*:*:*:*:*:*\",\"matchCriteriaId\":\"BB176AC3-3CDA-4DDA-9089-C67B2F73AA62\"},{\"vulnerable\":true,\"criteria\":\"cpe:2.3:a:fedoraproject:extra_packages_for_enterprise_linux:9.0:*:*:*:*:*:*:*\",\"matchCriteriaId\":\"3C30C1AC-01E4-4D7C-B03A-8EEEF3FC8C2F\"},{\"vulnerable\":true,\"criteria\":\"cpe:2.3:o:fedoraproject:fedora:38:*:*:*:*:*:*:*\",\"matchCriteriaId\":\"CC559B26-5DFC-4B7A-A27C-B77DE755DFF9\"},{\"vulnerable\":true,\"criteria\":\"cpe:2.3:o:fedoraproject:fedora:39:*:*:*:*:*:*:*\",\"matchCriteriaId\":\"B8EDB836-4E6A-4B71-B9B2-AA3E03E0F646\"}]}]},{\"nodes\":[{\"operator\":\"OR\",\"negate\":false,\"cpeMatch\":[{\"vulnerable\":true,\"criteria\":\"cpe:2.3:o:debian:debian_linux:10.0:*:*:*:*:*:*:*\",\"matchCriteriaId\":\"07B237A9-69A3-4A9C-9DA0-4E06BD37AE73\"}]}]}],\"references\":[{\"url\":\"http://www.openwall.com/lists/oss-security/2023/12/24/1\",\"source\":\"cve@mitre.org\",\"tags\":[\"Mailing List\",\"Third Party Advisory\"]},{\"url\":\"http://www.openwall.com/lists/oss-security/2023/12/25/1\",\"source\":\"cve@mitre.org\",\"tags\":[\"Mailing List\",\"Third Party Advisory\"]},{\"url\":\"http://www.openwall.com/lists/oss-security/2023/12/29/2\",\"source\":\"cve@mitre.org\",\"tags\":[\"Mailing List\",\"Mitigation\",\"Third Party Advisory\"]},{\"url\":\"http://www.openwall.com/lists/oss-security/2024/01/01/1\",\"source\":\"cve@mitre.org\",\"tags\":[\"Mailing List\",\"Third Party Advisory\"]},{\"url\":\"http://www.openwall.com/lists/oss-security/2024/01/01/2\",\"source\":\"cve@mitre.org\",\"tags\":[\"Mailing List\",\"Third Party Advisory\"]},{\"url\":\"http://www.openwall.com/lists/oss-security/2024/01/01/3\",\"source\":\"cve@mitre.org\",\"tags\":[\"Mailing List\",\"Third Party Advisory\"]},{\"url\":\"https://bugs.exim.org/show_bug.cgi?id=3063\",\"source\":\"cve@mitre.org\",\"tags\":[\"Issue Tracking\",\"Vendor 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Advisory\"]},{\"url\":\"https://www.openwall.com/lists/oss-security/2023/12/23/2\",\"source\":\"cve@mitre.org\",\"tags\":[\"Issue Tracking\",\"Mailing List\",\"Third Party Advisory\"]},{\"url\":\"https://www.youtube.com/watch?v=V8KPV96g1To\",\"source\":\"cve@mitre.org\",\"tags\":[\"Exploit\"]},{\"url\":\"http://www.openwall.com/lists/oss-security/2023/12/24/1\",\"source\":\"af854a3a-2127-422b-91ae-364da2661108\",\"tags\":[\"Mailing List\",\"Third Party Advisory\"]},{\"url\":\"http://www.openwall.com/lists/oss-security/2023/12/25/1\",\"source\":\"af854a3a-2127-422b-91ae-364da2661108\",\"tags\":[\"Mailing List\",\"Third Party Advisory\"]},{\"url\":\"http://www.openwall.com/lists/oss-security/2023/12/29/2\",\"source\":\"af854a3a-2127-422b-91ae-364da2661108\",\"tags\":[\"Mailing List\",\"Mitigation\",\"Third Party Advisory\"]},{\"url\":\"http://www.openwall.com/lists/oss-security/2024/01/01/1\",\"source\":\"af854a3a-2127-422b-91ae-364da2661108\",\"tags\":[\"Mailing List\",\"Third Party Advisory\"]},{\"url\":\"http://www.openwall.com/lists/oss-security/2024/01/01/2\",\"source\":\"af854a3a-2127-422b-91ae-364da2661108\",\"tags\":[\"Mailing List\",\"Third Party Advisory\"]},{\"url\":\"http://www.openwall.com/lists/oss-security/2024/01/01/3\",\"source\":\"af854a3a-2127-422b-91ae-364da2661108\",\"tags\":[\"Mailing List\",\"Third Party Advisory\"]},{\"url\":\"https://bugs.exim.org/show_bug.cgi?id=3063\",\"source\":\"af854a3a-2127-422b-91ae-364da2661108\",\"tags\":[\"Issue Tracking\",\"Vendor Advisory\"]},{\"url\":\"https://bugzilla.redhat.com/show_bug.cgi?id=2255852\",\"source\":\"af854a3a-2127-422b-91ae-364da2661108\",\"tags\":[\"Issue Tracking\",\"Third Party Advisory\"]},{\"url\":\"https://exim.org/static/doc/security/CVE-2023-51766.txt\",\"source\":\"af854a3a-2127-422b-91ae-364da2661108\",\"tags\":[\"Broken 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Advisory\"]},{\"url\":\"https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/ORN7OKEQPPBKUHYRQ6LR5PSNBQVDHAWB/\",\"source\":\"af854a3a-2127-422b-91ae-364da2661108\",\"tags\":[\"Mailing List\",\"Third Party Advisory\"]},{\"url\":\"https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/QPDWHJPABVJCXDSNELSSVTIVAJU2MDUQ/\",\"source\":\"af854a3a-2127-422b-91ae-364da2661108\",\"tags\":[\"Mailing List\",\"Third Party Advisory\"]},{\"url\":\"https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/ORN7OKEQPPBKUHYRQ6LR5PSNBQVDHAWB/\",\"source\":\"af854a3a-2127-422b-91ae-364da2661108\"},{\"url\":\"https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/QPDWHJPABVJCXDSNELSSVTIVAJU2MDUQ/\",\"source\":\"af854a3a-2127-422b-91ae-364da2661108\"},{\"url\":\"https://lwn.net/Articles/956533/\",\"source\":\"af854a3a-2127-422b-91ae-364da2661108\",\"tags\":[\"Third Party Advisory\"]},{\"url\":\"https://sec-consult.com/blog/detail/smtp-smuggling-spoofing-e-mails-worldwide/\",\"source\":\"af854a3a-2127-422b-91ae-364da2661108\",\"tags\":[\"Technical Description\",\"Third Party Advisory\"]},{\"url\":\"https://www.openwall.com/lists/oss-security/2023/12/23/2\",\"source\":\"af854a3a-2127-422b-91ae-364da2661108\",\"tags\":[\"Issue Tracking\",\"Mailing List\",\"Third Party Advisory\"]},{\"url\":\"https://www.youtube.com/watch?v=V8KPV96g1To\",\"source\":\"af854a3a-2127-422b-91ae-364da2661108\",\"tags\":[\"Exploit\"]}]}}",
    "redhat_vex": {
      "current_release_date": "2026-06-26T08:59:19+00:00",
      "cve": "CVE-2023-51766",
      "id": "CVE-2023-51766",
      "initial_release_date": "2023-12-24T00:00:00+00:00",
      "product_status:known_not_affected": "1",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "exim: SMTP smuggling vulnerability",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2023/cve-2023-51766.json",
      "version": "3"
    },
    "suse_vex": {
      "aggregate_severity": "moderate",
      "current_release_date": "2025-03-15T06:03:00Z",
      "cve": "CVE-2023-51766",
      "id": "CVE-2023-51766",
      "initial_release_date": "2023-12-25T02:10:52Z",
      "product_status:recommended": "9",
      "source": "SUSE CSAF VEX",
      "status": "interim",
      "title": "SUSE CVE CVE-2023-51766",
      "url": "https://ftp.suse.com/pub/projects/security/csaf-vex/cve-2023-51766.json",
      "version": "10"
    }
  }
}



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Taxonomy of the tags.





Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

Sightings

Author Source Type Date Other

Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
  • Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
  • Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
  • Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
  • Not confirmed: The user expressed doubt about the validity of the vulnerability.
  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.


Detection rules are retrieved from Rulezet.