{"id":"UBUNTU-CVE-2026-40203","details":"When IMAP compression is enabled, the same compression state is reused across responses in a session, so response sizes depend on both attacker-supplied mail and other mail in the same mailbox. An attacker that can send mail to a user and can also observe the sizes of that user's IMAP traffic can confirm whether the body of a small message matches a guessed text. Recovery of arbitrary unknown content was not demonstrated, but the attack can disclose whether a secret-like message body matches a candidate. Disable IMAP compression. Update to non-vulnerable version. No publicly available exploits are known.","modified":"2026-09-02T19:36:04.729357484Z","published":"2026-08-28T00:00:00Z","upstream":["CVE-2026-40203"],"references":[{"type":"REPORT","url":"https://ubuntu.com/security/CVE-2026-40203"},{"type":"REPORT","url":"https://www.cve.org/CVERecord?id=CVE-2026-40203"}],"affected":[{"package":{"name":"dovecot","ecosystem":"Ubuntu:Pro:14.04:LTS","purl":"pkg:deb/ubuntu/dovecot?arch=source&distro=esm-infra-legacy%2Ftrusty"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["1:2.1.7-7ubuntu3","1:2.2.9-1ubuntu1","1:2.2.9-1ubuntu2","1:2.2.9-1ubuntu2.1","1:2.2.9-1ubuntu2.3","1:2.2.9-1ubuntu2.4","1:2.2.9-1ubuntu2.5","1:2.2.9-1ubuntu2.6","1:2.2.9-1ubuntu2.6+esm1","1:2.2.9-1ubuntu2.6+esm2","1:2.2.9-1ubuntu2.6+esm3","1:2.2.9-1ubuntu2.6+esm4"],"ecosystem_specific":{"binaries":[{"binary_name":"dovecot-core","binary_version":"1:2.2.9-1ubuntu2.6+esm4"},{"binary_name":"dovecot-gssapi","binary_version":"1:2.2.9-1ubuntu2.6+esm4"},{"binary_version":"1:2.2.9-1ubuntu2.6+esm4","binary_name":"dovecot-imapd"},{"binary_name":"dovecot-ldap","binary_version":"1:2.2.9-1ubuntu2.6+esm4"},{"binary_version":"1:2.2.9-1ubuntu2.6+esm4","binary_name":"dovecot-lmtpd"},{"binary_name":"dovecot-managesieved","binary_version":"1:2.2.9-1ubuntu2.6+esm4"},{"binary_name":"dovecot-mysql","binary_version":"1:2.2.9-1ubuntu2.6+esm4"},{"binary_name":"dovecot-pgsql","binary_version":"1:2.2.9-1ubuntu2.6+esm4"},{"binary_name":"dovecot-pop3d","binary_version":"1:2.2.9-1ubuntu2.6+esm4"},{"binary_name":"dovecot-sieve","binary_version":"1:2.2.9-1ubuntu2.6+esm4"},{"binary_name":"dovecot-solr","binary_version":"1:2.2.9-1ubuntu2.6+esm4"},{"binary_name":"dovecot-sqlite","binary_version":"1:2.2.9-1ubuntu2.6+esm4"},{"binary_name":"mail-stack-delivery","binary_version":"1:2.2.9-1ubuntu2.6+esm4"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-40203.json"}},{"package":{"name":"dovecot","ecosystem":"Ubuntu:16.04:LTS","purl":"pkg:deb/ubuntu/dovecot?arch=source&distro=xenial"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["1:2.2.18-2ubuntu2","1:2.2.22-1ubuntu1","1:2.2.22-1ubuntu2","1:2.2.22-1ubuntu2.1","1:2.2.22-1ubuntu2.2","1:2.2.22-1ubuntu2.3","1:2.2.22-1ubuntu2.4","1:2.2.22-1ubuntu2.6","1:2.2.22-1ubuntu2.7","1:2.2.22-1ubuntu2.8","1:2.2.22-1ubuntu2.9","1:2.2.22-1ubuntu2.10","1:2.2.22-1ubuntu2.11","1:2.2.22-1ubuntu2.12","1:2.2.22-1ubuntu2.13","1:2.2.22-1ubuntu2.14"],"ecosystem_specific":{"binaries":[{"binary_name":"dovecot-core","binary_version":"1:2.2.22-1ubuntu2.14"},{"binary_version":"1:2.2.22-1ubuntu2.14","binary_name":"dovecot-gssapi"},{"binary_version":"1:2.2.22-1ubuntu2.14","binary_name":"dovecot-imapd"},{"binary_name":"dovecot-ldap","binary_version":"1:2.2.22-1ubuntu2.14"},{"binary_version":"1:2.2.22-1ubuntu2.14","binary_name":"dovecot-lmtpd"},{"binary_version":"1:2.2.22-1ubuntu2.14","binary_name":"dovecot-lucene"},{"binary_name":"dovecot-managesieved","binary_version":"1:2.2.22-1ubuntu2.14"},{"binary_version":"1:2.2.22-1ubuntu2.14","binary_name":"dovecot-mysql"},{"binary_version":"1:2.2.22-1ubuntu2.14","binary_name":"dovecot-pgsql"},{"binary_name":"dovecot-pop3d","binary_version":"1:2.2.22-1ubuntu2.14"},{"binary_name":"dovecot-sieve","binary_version":"1:2.2.22-1ubuntu2.14"},{"binary_name":"dovecot-solr","binary_version":"1:2.2.22-1ubuntu2.14"},{"binary_version":"1:2.2.22-1ubuntu2.14","binary_name":"dovecot-sqlite"},{"binary_name":"mail-stack-delivery","binary_version":"1:2.2.22-1ubuntu2.14"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-40203.json"}},{"package":{"name":"dovecot","ecosystem":"Ubuntu:18.04:LTS","purl":"pkg:deb/ubuntu/dovecot?arch=source&distro=bionic"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["1:2.2.27-3ubuntu1","1:2.2.33.2-1ubuntu1","1:2.2.33.2-1ubuntu2","1:2.2.33.2-1ubuntu3","1:2.2.33.2-1ubuntu4","1:2.2.33.2-1ubuntu4.1","1:2.2.33.2-1ubuntu4.2","1:2.2.33.2-1ubuntu4.3","1:2.2.33.2-1ubuntu4.4","1:2.2.33.2-1ubuntu4.5","1:2.2.33.2-1ubuntu4.6","1:2.2.33.2-1ubuntu4.7","1:2.2.33.2-1ubuntu4.8"],"ecosystem_specific":{"binaries":[{"binary_version":"1:2.2.33.2-1ubuntu4.8","binary_name":"dovecot-core"},{"binary_name":"dovecot-gssapi","binary_version":"1:2.2.33.2-1ubuntu4.8"},{"binary_name":"dovecot-imapd","binary_version":"1:2.2.33.2-1ubuntu4.8"},{"binary_name":"dovecot-ldap","binary_version":"1:2.2.33.2-1ubuntu4.8"},{"binary_name":"dovecot-lmtpd","binary_version":"1:2.2.33.2-1ubuntu4.8"},{"binary_name":"dovecot-managesieved","binary_version":"1:2.2.33.2-1ubuntu4.8"},{"binary_version":"1:2.2.33.2-1ubuntu4.8","binary_name":"dovecot-mysql"},{"binary_name":"dovecot-pgsql","binary_version":"1:2.2.33.2-1ubuntu4.8"},{"binary_name":"dovecot-pop3d","binary_version":"1:2.2.33.2-1ubuntu4.8"},{"binary_name":"dovecot-sieve","binary_version":"1:2.2.33.2-1ubuntu4.8"},{"binary_name":"dovecot-solr","binary_version":"1:2.2.33.2-1ubuntu4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