{"id":"UBUNTU-CVE-2023-51766","details":"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.","modified":"2026-06-04T02:14:19.334173283Z","published":"2023-12-24T06:15:00Z","related":["USN-6611-1","USN-8382-1"],"upstream":["CVE-2023-51766"],"references":[{"type":"REPORT","url":"https://ubuntu.com/security/CVE-2023-51766"},{"type":"REPORT","url":"https://sec-consult.com/blog/detail/smtp-smuggling-spoofing-e-mails-worldwide/"},{"type":"REPORT","url":"https://www.openwall.com/lists/oss-security/2023/12/21/6"},{"type":"REPORT","url":"https://exim.org/static/doc/security/CVE-2023-51766.txt"},{"type":"REPORT","url":"https://git.exim.org/exim.git/commit/cf1376206284f2a4f11e32d931d4aade34c206c5"},{"type":"REPORT","url":"https://git.exim.org/exim.git/commit/4596719398f6f2365bed563aafd757a6433ce7b4"},{"type":"REPORT","url":"https://git.exim.org/exim.git/commit/5bb786d5ad568a88d50d15452aacc8404047e5ca"},{"type":"ADVISORY","url":"https://ubuntu.com/security/notices/USN-6611-1"},{"type":"REPORT","url":"https://www.cve.org/CVERecord?id=CVE-2023-51766"},{"type":"ADVISORY","url":"https://ubuntu.com/security/notices/USN-8382-1"}],"affected":[{"package":{"name":"exim4","ecosystem":"Ubuntu:Pro:14.04:LTS","purl":"pkg:deb/ubuntu/exim4?arch=source&distro=esm-infra-legacy%2Ftrusty"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"4.82-3ubuntu2.4+esm9"}]}],"versions":["4.80-7ubuntu3","4.80-7ubuntu4","4.80-9ubuntu1","4.80-9ubuntu2","4.82-3ubuntu1","4.82-3ubuntu2","4.82-3ubuntu2.1","4.82-3ubuntu2.2","4.82-3ubuntu2.3","4.82-3ubuntu2.4","4.82-3ubuntu2.4+esm1","4.82-3ubuntu2.4+esm2","4.82-3ubuntu2.4+esm3","4.82-3ubuntu2.4+esm4","4.82-3ubuntu2.4+esm6","4.82-3ubuntu2.4+esm7","4.82-3ubuntu2.4+esm8"],"ecosystem_specific":{"binaries":[{"binary_name":"exim4","binary_version":"4.82-3ubuntu2.4+esm9"},{"binary_name":"exim4-base","binary_version":"4.82-3ubuntu2.4+esm9"},{"binary_name":"exim4-config","binary_version":"4.82-3ubuntu2.4+esm9"},{"binary_version":"4.82-3ubuntu2.4+esm9","binary_name":"exim4-daemon-heavy"},{"binary_name":"exim4-daemon-light","binary_version":"4.82-3ubuntu2.4+esm9"},{"binary_version":"4.82-3ubuntu2.4+esm9","binary_name":"eximon4"}],"availability":"Available with Ubuntu Pro with Legacy support add-on: https://ubuntu.com/pro"},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2023/UBUNTU-CVE-2023-51766.json"}},{"package":{"name":"exim4","ecosystem":"Ubuntu:Pro:16.04:LTS","purl":"pkg:deb/ubuntu/exim4?arch=source&distro=esm-infra%2Fxenial"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"4.86.2-2ubuntu2.6+esm6"}]}],"versions":["4.86-3ubuntu1","4.86-7ubuntu1","4.86-7ubuntu2","4.86-7ubuntu3","4.86.2-2ubuntu1","4.86.2-2ubuntu2","4.86.2-2ubuntu2.1","4.86.2-2ubuntu2.2","4.86.2-2ubuntu2.3","4.86.2-2ubuntu2.4","4.86.2-2ubuntu2.5","4.86.2-2ubuntu2.6","4.86.2-2ubuntu2.6+esm1","4.86.2-2ubuntu2.6+esm2","4.86.2-2ubuntu2.6+esm4","4.86.2-2ubuntu2.6+esm5"],"ecosystem_specific":{"binaries":[{"binary_name":"exim4","binary_version":"4.86.2-2ubuntu2.6+esm6"},{"binary_name":"exim4-base","binary_version":"4.86.2-2ubuntu2.6+esm6"},{"binary_name":"exim4-config","binary_version":"4.86.2-2ubuntu2.6+esm6"},{"binary_version":"4.86.2-2ubuntu2.6+esm6","binary_name":"exim4-daemon-heavy"},{"binary_version":"4.86.2-2ubuntu2.6+esm6","binary_name":"exim4-daemon-light"},{"binary_name":"eximon4","binary_version":"4.86.2-2ubuntu2.6+esm6"}],"availability":"Available with Ubuntu Pro (Infra-only): https://ubuntu.com/pro"},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2023/UBUNTU-CVE-2023-51766.json"}},{"package":{"name":"exim4","ecosystem":"Ubuntu:Pro:18.04:LTS","purl":"pkg:deb/ubuntu/exim4?arch=source&distro=esm-infra%2Fbionic"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"4.90.1-1ubuntu1.10+esm3"}]}],"versions":["4.89-5ubuntu1","4.89-9ubuntu1","4.89-9ubuntu2","4.89-9ubuntu3","4.89-9ubuntu4","4.90.1-1ubuntu1","4.90.1-1ubuntu1.1","4.90.1-1ubuntu1.2","4.90.1-1ubuntu1.3","4.90.1-1ubuntu1.4","4.90.1-1ubuntu1.5","4.90.1-1ubuntu1.8","4.90.1-1ubuntu1.9","4.90.1-1ubuntu1.10","4.90.1-1ubuntu1.10+esm1","4.90.1-1ubuntu1.10+esm2"],"ecosystem_specific":{"binaries":[{"binary_name":"exim4","binary_version":"4.90.1-1ubuntu1.10+esm3"},{"binary_version":"4.90.1-1ubuntu1.10+esm3","binary_name":"exim4-base"},{"binary_name":"exim4-config","binary_version":"4.90.1-1ubuntu1.10+esm3"},{"binary_version":"4.90.1-1ubuntu1.10+esm3","binary_name":"exim4-daemon-heavy"},{"binary_version":"4.90.1-1ubuntu1.10+esm3","binary_name":"exim4-daemon-light"},{"binary_name":"eximon4","binary_version":"4.90.1-1ubuntu1.10+esm3"}],"availability":"Available with Ubuntu Pro (Infra-only): https://ubuntu.com/pro"},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2023/UBUNTU-CVE-2023-51766.json"}},{"package":{"name":"exim4","ecosystem":"Ubuntu:20.04:LTS","purl":"pkg:deb/ubuntu/exim4?arch=source&distro=focal"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"4.93-13ubuntu1.10"}]}],"versions":["4.92.1-1ubuntu3","4.92.1-1ubuntu4","4.93~RC2-1ubuntu1","4.93-9ubuntu1","4.93-11ubuntu1","4.93-12ubuntu1","4.93-13ubuntu1","4.93-13ubuntu1.1","4.93-13ubuntu1.5","4.93-13ubuntu1.6","4.93-13ubuntu1.7","4.93-13ubuntu1.8","4.93-13ubuntu1.9"],"ecosystem_specific":{"availability":"No subscription required","binaries":[{"binary_name":"exim4","binary_version":"4.93-13ubuntu1.10"},{"binary_name":"exim4-base","binary_version":"4.93-13ubuntu1.10"},{"binary_name":"exim4-config","binary_version":"4.93-13ubuntu1.10"},{"binary_version":"4.93-13ubuntu1.10","binary_name":"exim4-daemon-heavy"},{"binary_version":"4.93-13ubuntu1.10","binary_name":"exim4-daemon-light"},{"binary_name":"eximon4","binary_version":"4.93-13ubuntu1.10"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2023/UBUNTU-CVE-2023-51766.json"}},{"package":{"name":"exim4","ecosystem":"Ubuntu:22.04:LTS","purl":"pkg:deb/ubuntu/exim4?arch=source&distro=jammy"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"4.95-4ubuntu2.5"}]}],"versions":["4.94.2-7ubuntu2","4.95-2ubuntu2","4.95-4ubuntu1","4.95-4ubuntu2","4.95-4ubuntu2.1","4.95-4ubuntu2.2","4.95-4ubuntu2.3","4.95-4ubuntu2.4"],"ecosystem_specific":{"binaries":[{"binary_version":"4.95-4ubuntu2.5","binary_name":"exim4"},{"binary_version":"4.95-4ubuntu2.5","binary_name":"exim4-base"},{"binary_version":"4.95-4ubuntu2.5","binary_name":"exim4-config"},{"binary_name":"exim4-daemon-heavy","binary_version":"4.95-4ubuntu2.5"},{"binary_version":"4.95-4ubuntu2.5","binary_name":"exim4-daemon-light"},{"binary_name":"eximon4","binary_version":"4.95-4ubuntu2.5"}],"availability":"No subscription required"},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2023/UBUNTU-CVE-2023-51766.json"}}],"schema_version":"1.7.5","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N"},{"type":"Ubuntu","score":"medium"}]}