{"id":"CVE-2026-40203","state":"PUBLISHED","title":"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 ","description":"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.","publishedAt":"2026-08-28T10:12:22.287Z","updatedAt":"2026-08-28T14:57:07.686Z","severity":{"score":3.7,"label":"Low","version":"3.1","vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N","source":"OX"},"assigner":"OX","products":["Open-Xchange GmbH OX Dovecot Pro","Open-Xchange GmbH OX Dovecot CE"],"affected":[{"vendor":"Open-Xchange GmbH","product":"OX Dovecot Pro","defaultStatus":"unaffected","versions":[{"version":"2.3.0","status":"affected","lessThan":"2.3.22.2","versionType":"semver"},{"version":"3.0.0","status":"affected","lessThan":"3.0.7","versionType":"semver"},{"version":"3.1.0","status":"affected","lessThan":"3.1.6","versionType":"semver"}],"modules":["core"]},{"vendor":"Open-Xchange GmbH","product":"OX Dovecot CE","defaultStatus":"unaffected","versions":[{"version":"2.3.0","status":"affected","lessThan":"2.4.5","versionType":"semver"}],"modules":["core"]}],"references":["https://documentation.open-xchange.com/dovecot/security/advisories/csaf/2026/oxdc-adv-2026-0003.json"],"weaknesses":["CWE-200"],"ingestedAt":"2026-10-29T20:11:57.932Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/40xxx/CVE-2026-40203.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-40203","state":"PUBLISHED","datePublished":"2026-08-28T10:12:22.287Z","dateUpdated":"2026-08-28T14:57:07.686Z","assignerShortName":"OX","assignerOrgId":"8ce71d90-2354-404b-a86e-bec2cc4e6981","dateReserved":"2026-04-10T07:11:39.060Z"},"containers":{"cna":{"descriptions":[{"lang":"en","value":"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."}],"affected":[{"vendor":"Open-Xchange GmbH","product":"OX Dovecot Pro","defaultStatus":"unaffected","versions":[{"version":"2.3.0","status":"affected","lessThan":"2.3.22.2","versionType":"semver"},{"version":"3.0.0","status":"affected","lessThan":"3.0.7","versionType":"semver"},{"version":"3.1.0","status":"affected","lessThan":"3.1.6","versionType":"semver"}],"modules":["core"]},{"vendor":"Open-Xchange GmbH","product":"OX Dovecot CE","defaultStatus":"unaffected","versions":[{"version":"2.3.0","status":"affected","lessThan":"2.4.5","versionType":"semver"}],"modules":["core"]}],"references":[{"url":"https://documentation.open-xchange.com/dovecot/security/advisories/csaf/2026/oxdc-adv-2026-0003.json","tags":["vendor-advisory"]}],"metrics":[{"cvssV3_1":{"attackComplexity":"HIGH","attackVector":"NETWORK","availabilityImpact":"NONE","baseScore":3.7,"baseSeverity":"LOW","confidentialityImpact":"LOW","integrityImpact":"NONE","privilegesRequired":"NONE","scope":"UNCHANGED","userInteraction":"NONE","vectorString":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N","version":"3.1"},"format":"CVSS","scenarios":[{"lang":"en","value":"GENERAL"}]}],"problemTypes":[{"descriptions":[{"cweId":"CWE-200","description":"Exposure of Sensitive Information to an Unauthorized Actor","lang":"en","type":"cwe"}]}],"providerMetadata":{"shortName":"OX","orgId":"8ce71d90-2354-404b-a86e-bec2cc4e6981","dateUpdated":"2026-08-28T10:30:48.341Z"},"source":{"defect":"DOV-9066","discovery":"EXTERNAL"}},"adp":[{"title":"CISA ADP Vulnrichment","metrics":[{"other":{"type":"ssvc","content":{"timestamp":"2026-08-28T14:56:57.150012Z","id":"CVE-2026-40203","options":[{"Exploitation":"none"},{"Automatable":"no"},{"Technical Impact":"partial"}],"role":"CISA Coordinator","version":"2.0.3"}}}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2026-08-28T14:57:07.686Z"}}]}}}