{"id":"DEBIAN-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":"2026-09-14T17:03:10.201495396Z","published":"2026-08-28T12:16:28.897Z","upstream":["CVE-2026-40203"],"references":[{"type":"ADVISORY","url":"https://security-tracker.debian.org/tracker/CVE-2026-40203"}],"affected":[{"package":{"name":"dovecot","ecosystem":"Debian:12","purl":"pkg:deb/debian/dovecot?arch=source&distro=bookworm"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["1:2.3.19.1+dfsg1-2.1","1:2.3.19.1+dfsg1-2.1+deb12u1","1:2.3.19.1+dfsg1-2.1+deb12u2","1:2.3.19.1+dfsg1-2.1+deb12u3","1:2.3.19.1+dfsg1-2.1+deb12u4","1:2.3.19.1+dfsg1-2.1+deb12u5","1:2.3.19.1+dfsg1-2.1+deb12u6","1:2.3.20+dfsg1-1","1:2.3.21+dfsg1-1","1:2.3.21+dfsg1-2","1:2.3.21+dfsg1-3","1:2.3.21+dfsg1-3~bpo12+1","1:2.3.21.1+dfsg1-1","1:2.3.21.1+dfsg1-1~bpo12+1","1:2.4.0+dfsg1-1~exp1","1:2.4.0+dfsg1-1~exp2","1:2.4.0+dfsg1-1~exp3","1:2.4.0+dfsg1-1~exp4","1:2.4.0+dfsg1-1~exp5","1:2.4.0+dfsg1-1~exp6","1:2.4.1+dfsg1-1","1:2.4.1+dfsg1-1~exp1","1:2.4.1+dfsg1-1~exp2","1:2.4.1+dfsg1-2","1:2.4.1+dfsg1-3","1:2.4.1+dfsg1-4","1:2.4.1+dfsg1-5","1:2.4.1+dfsg1-6","1:2.4.1+dfsg1-6~exp1","1:2.4.1+dfsg1-7","1:2.4.1+dfsg1-8","1:2.4.1+dfsg1-9","1:2.4.2+dfsg1-1","1:2.4.2+dfsg1-2","1:2.4.2+dfsg1-3","1:2.4.2+dfsg1-4","1:2.4.3+dfsg1-1","1:2.4.3+dfsg1-2","1:2.4.4+dfsg1-1","1:2.4.4+dfsg1-2","1:2.4.5+dfsg1-1","1:2.4.5+dfsg1-2"],"ecosystem_specific":{"urgency":"not yet assigned"},"database_specific":{"source":"https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2026-40203.json"}},{"package":{"name":"dovecot","ecosystem":"Debian:13","purl":"pkg:deb/debian/dovecot?arch=source&distro=trixie"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["1:2.4.1+dfsg1-6","1:2.4.1+dfsg1-6+deb13u1","1:2.4.1+dfsg1-6+deb13u2","1:2.4.1+dfsg1-6+deb13u3","1:2.4.1+dfsg1-6+deb13u4","1:2.4.1+dfsg1-6+deb13u5","1:2.4.1+dfsg1-6+deb13u6","1:2.4.1+dfsg1-7","1:2.4.1+dfsg1-8","1:2.4.1+dfsg1-9","1:2.4.2+dfsg1-1","1:2.4.2+dfsg1-2","1:2.4.2+dfsg1-3","1:2.4.2+dfsg1-4","1:2.4.3+dfsg1-1","1:2.4.3+dfsg1-2","1:2.4.4+dfsg1-1","1:2.4.4+dfsg1-2","1:2.4.5+dfsg1-1","1:2.4.5+dfsg1-2"],"ecosystem_specific":{"urgency":"not yet assigned"},"database_specific":{"source":"https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2026-40203.json"}},{"package":{"name":"dovecot","ecosystem":"Debian:14","purl":"pkg:deb/debian/dovecot?arch=source&distro=forky"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1:2.4.5+dfsg1-1"}]}],"versions":["1:2.4.1+dfsg1-6","1:2.4.1+dfsg1-7","1:2.4.1+dfsg1-8","1:2.4.1+dfsg1-9","1:2.4.2+dfsg1-1","1:2.4.2+dfsg1-2","1:2.4.2+dfsg1-3","1:2.4.2+dfsg1-4","1:2.4.3+dfsg1-1","1:2.4.3+dfsg1-2","1:2.4.4+dfsg1-1","1:2.4.4+dfsg1-2"],"ecosystem_specific":{"urgency":"not yet assigned"},"database_specific":{"source":"https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2026-40203.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N"}]}