{"id":"UBUNTU-CVE-2021-47865","details":"ProFTPD 1.3.7a contains a denial of service vulnerability that allows attackers to overwhelm the server by creating multiple simultaneous FTP connections. Attackers can repeatedly establish connections using threading to exhaust server connection limits and block legitimate user access.","modified":"2026-05-20T16:07:26.546278804Z","published":"2026-01-21T18:16:00Z","upstream":["CVE-2021-47865"],"references":[{"type":"REPORT","url":"https://ubuntu.com/security/CVE-2021-47865"},{"type":"REPORT","url":"https://www.cve.org/CVERecord?id=CVE-2021-47865"},{"type":"REPORT","url":"http://www.proftpd.org/"},{"type":"REPORT","url":"https://github.com/proftpd/proftpd"},{"type":"REPORT","url":"https://www.exploit-db.com/exploits/49697"},{"type":"REPORT","url":"https://www.vulncheck.com/advisories/proftpd-a-remote-denial-of-service"}],"affected":[{"package":{"name":"proftpd-dfsg","ecosystem":"Ubuntu:16.04:LTS","purl":"pkg:deb/ubuntu/proftpd-dfsg?arch=source&distro=xenial"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["1.3.5-2","1.3.5a-1","1.3.5a-1build1","1.3.5a-1ubuntu0.1"],"ecosystem_specific":{"binaries":[{"binary_version":"1.3.5a-1ubuntu0.1","binary_name":"proftpd-basic"},{"binary_version":"1.3.5a-1ubuntu0.1","binary_name":"proftpd-mod-geoip"},{"binary_version":"1.3.5a-1ubuntu0.1","binary_name":"proftpd-mod-ldap"},{"binary_version":"1.3.5a-1ubuntu0.1","binary_name":"proftpd-mod-mysql"},{"binary_version":"1.3.5a-1ubuntu0.1","binary_name":"proftpd-mod-odbc"},{"binary_name":"proftpd-mod-pgsql","binary_version":"1.3.5a-1ubuntu0.1"},{"binary_name":"proftpd-mod-sqlite","binary_version":"1.3.5a-1ubuntu0.1"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2021/UBUNTU-CVE-2021-47865.json"}},{"package":{"name":"proftpd-dfsg","ecosystem":"Ubuntu:18.04:LTS","purl":"pkg:deb/ubuntu/proftpd-dfsg?arch=source&distro=bionic"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["1.3.5d-1","1.3.5e-1build1"],"ecosystem_specific":{"binaries":[{"binary_name":"proftpd-basic","binary_version":"1.3.5e-1build1"},{"binary_name":"proftpd-mod-geoip","binary_version":"1.3.5e-1build1"},{"binary_name":"proftpd-mod-ldap","binary_version":"1.3.5e-1build1"},{"binary_version":"1.3.5e-1build1","binary_name":"proftpd-mod-mysql"},{"binary_name":"proftpd-mod-odbc","binary_version":"1.3.5e-1build1"},{"binary_name":"proftpd-mod-pgsql","binary_version":"1.3.5e-1build1"},{"binary_name":"proftpd-mod-sqlite","binary_version":"1.3.5e-1build1"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2021/UBUNTU-CVE-2021-47865.json"}},{"package":{"name":"proftpd-dfsg","ecosystem":"Ubuntu:20.04:LTS","purl":"pkg:deb/ubuntu/proftpd-dfsg?arch=source&distro=focal"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["1.3.6-6build2","1.3.6c-1","1.3.6c-2","1.3.6c-2ubuntu0.1"],"ecosystem_specific":{"binaries":[{"binary_name":"proftpd-basic","binary_version":"1.3.6c-2ubuntu0.1"},{"binary_version":"1.3.6c-2ubuntu0.1","binary_name":"proftpd-mod-geoip"},{"binary_name":"proftpd-mod-ldap","binary_version":"1.3.6c-2ubuntu0.1"},{"binary_version":"1.3.6c-2ubuntu0.1","binary_name":"proftpd-mod-mysql"},{"binary_name":"proftpd-mod-odbc","binary_version":"1.3.6c-2ubuntu0.1"},{"binary_name":"proftpd-mod-pgsql","binary_version":"1.3.6c-2ubuntu0.1"},{"binary_version":"1.3.6c-2ubuntu0.1","binary_name":"proftpd-mod-snmp"},{"binary_version":"1.3.6c-2ubuntu0.1","binary_name":"proftpd-mod-sqlite"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2021/UBUNTU-CVE-2021-47865.json"}},{"package":{"name":"proftpd-dfsg","ecosystem":"Ubuntu:22.04:LTS","purl":"pkg:deb/ubuntu/proftpd-dfsg?arch=source&distro=jammy"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["1.3.7b+dfsg-1","1.3.7c+dfsg-1build1","1.3.7c+dfsg-1ubuntu0.1"],"ecosystem_specific":{"binaries":[{"binary_name":"proftpd-basic","binary_version":"1.3.7c+dfsg-1ubuntu0.1"},{"binary_name":"proftpd-core","binary_version":"1.3.7c+dfsg-1ubuntu0.1"},{"binary_name":"proftpd-mod-crypto","binary_version":"1.3.7c+dfsg-1ubuntu0.1"},{"binary_name":"proftpd-mod-geoip","binary_version":"1.3.7c+dfsg-1ubuntu0.1"},{"binary_version":"1.3.7c+dfsg-1ubuntu0.1","binary_name":"proftpd-mod-ldap"},{"binary_name":"proftpd-mod-mysql","binary_version":"1.3.7c+dfsg-1ubuntu0.1"},{"binary_name":"proftpd-mod-odbc","binary_version":"1.3.7c+dfsg-1ubuntu0.1"},{"binary_version":"1.3.7c+dfsg-1ubuntu0.1","binary_name":"proftpd-mod-pgsql"},{"binary_version":"1.3.7c+dfsg-1ubuntu0.1","binary_name":"proftpd-mod-snmp"},{"binary_name":"proftpd-mod-sqlite","binary_version":"1.3.7c+dfsg-1ubuntu0.1"},{"binary_version":"1.3.7c+dfsg-1ubuntu0.1","binary_name":"proftpd-mod-wrap"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2021/UBUNTU-CVE-2021-47865.json"}},{"package":{"name":"proftpd-dfsg","ecosystem":"Ubuntu:24.04:LTS","purl":"pkg:deb/ubuntu/proftpd-dfsg?arch=source&distro=noble"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["1.3.8+dfsg-8","1.3.8.a+dfsg-1","1.3.8.b+dfsg-1","1.3.8.b+dfsg-1build1","1.3.8.b+dfsg-1build2","1.3.8.b+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