{"dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": {"cveId": "CVE-2026-40203", "assignerOrgId": "8ce71d90-2354-404b-a86e-bec2cc4e6981", "state": "PUBLISHED", "assignerShortName": "OX", "dateReserved": "2026-04-10T07:11:39.060Z", "datePublished": "2026-08-28T10:12:22.287Z", "dateUpdated": "2026-08-28T14:57:07.686Z"}, "containers": {"cna": {"affected": [{"defaultStatus": "unaffected", "modules": ["core"], "product": "OX Dovecot Pro", "vendor": "Open-Xchange GmbH", "versions": [{"lessThan": "2.3.22.2", "status": "affected", "version": "2.3.0", "versionType": "semver"}, {"lessThan": "3.0.7", "status": "affected", "version": "3.0.0", "versionType": "semver"}, {"lessThan": "3.1.6", "status": "affected", "version": "3.1.0", "versionType": "semver"}]}, {"defaultStatus": "unaffected", "modules": ["core"], "product": "OX Dovecot CE", "vendor": "Open-Xchange GmbH", "versions": [{"lessThan": "2.4.5", "status": "affected", "version": "2.3.0", "versionType": "semver"}]}], "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."}], "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": {"orgId": "8ce71d90-2354-404b-a86e-bec2cc4e6981", "shortName": "OX", "dateUpdated": "2026-08-28T10:30:48.341Z"}, "references": [{"tags": ["vendor-advisory"], "url": "https://documentation.open-xchange.com/dovecot/security/advisories/csaf/2026/oxdc-adv-2026-0003.json"}], "source": {"defect": "DOV-9066", "discovery": "EXTERNAL"}}, "adp": [{"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"}}}], "title": "CISA ADP Vulnrichment", "providerMetadata": {"orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "shortName": "CISA-ADP", "dateUpdated": "2026-08-28T14:57:07.686Z"}}]}}

{"dataType": "CVE_RECORD", "containers": {"adp": [{"title": "CISA ADP Vulnrichment", "metrics": [{"other": {"type": "ssvc", "content": {"id": "CVE-2026-40203", "role": "CISA Coordinator", "options": [{"Exploitation": "none"}, {"Automatable": "no"}, {"Technical Impact": "partial"}], "version": "2.0.3", "timestamp": "2026-08-28T14:56:57.150012Z"}}}], "providerMetadata": {"orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "shortName": "CISA-ADP", "dateUpdated": "2026-08-28T14:57:03.836Z"}}], "cna": {"source": {"defect": "DOV-9066", "discovery": "EXTERNAL"}, "metrics": [{"format": "CVSS", "cvssV3_1": {"scope": "UNCHANGED", "version": "3.1", "baseScore": 3.7, "attackVector": "NETWORK", "baseSeverity": "LOW", "vectorString": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N", "integrityImpact": "NONE", "userInteraction": "NONE", "attackComplexity": "HIGH", "availabilityImpact": "NONE", "privilegesRequired": "NONE", "confidentialityImpact": "LOW"}, "scenarios": [{"lang": "en", "value": "GENERAL"}]}], "affected": [{"vendor": "Open-Xchange GmbH", "modules": ["core"], "product": "OX Dovecot Pro", "versions": [{"status": "affected", "version": "2.3.0", "lessThan": "2.3.22.2", "versionType": "semver"}, {"status": "affected", "version": "3.0.0", "lessThan": "3.0.7", "versionType": "semver"}, {"status": "affected", "version": "3.1.0", "lessThan": "3.1.6", "versionType": "semver"}], "defaultStatus": "unaffected"}, {"vendor": "Open-Xchange GmbH", "modules": ["core"], "product": "OX Dovecot CE", "versions": [{"status": "affected", "version": "2.3.0", "lessThan": "2.4.5", "versionType": "semver"}], "defaultStatus": "unaffected"}], "references": [{"url": "https://documentation.open-xchange.com/dovecot/security/advisories/csaf/2026/oxdc-adv-2026-0003.json", "tags": ["vendor-advisory"]}], "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."}], "problemTypes": [{"descriptions": [{"lang": "en", "type": "cwe", "cweId": "CWE-200", "description": "Exposure of Sensitive Information to an Unauthorized Actor"}]}], "providerMetadata": {"orgId": "8ce71d90-2354-404b-a86e-bec2cc4e6981", "shortName": "OX", "dateUpdated": "2026-08-28T10:30:48.341Z"}}}, "cveMetadata": {"cveId": "CVE-2026-40203", "state": "PUBLISHED", "dateUpdated": "2026-08-28T14:57:07.686Z", "dateReserved": "2026-04-10T07:11:39.060Z", "assignerOrgId": "8ce71d90-2354-404b-a86e-bec2cc4e6981", "datePublished": "2026-08-28T10:12:22.287Z", "assignerShortName": "OX"}, "dataVersion": "5.2"}

{"affected": [{"affectedData": [{"defaultStatus": "unaffected", "modules": ["core"], "product": "OX Dovecot Pro", "vendor": "Open-Xchange GmbH", "versions": [{"lessThan": "2.3.22.2", "status": "affected", "version": "2.3.0", "versionType": "semver"}, {"lessThan": "3.0.7", "status": "affected", "version": "3.0.0", "versionType": "semver"}, {"lessThan": "3.1.6", "status": "affected", "version": "3.1.0", "versionType": "semver"}]}, {"defaultStatus": "unaffected", "modules": ["core"], "product": "OX Dovecot CE", "vendor": "Open-Xchange GmbH", "versions": [{"lessThan": "2.4.5", "status": "affected", "version": "2.3.0", "versionType": "semver"}]}], "source": "[email protected]"}], "cveTags": [], "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."}], "id": "CVE-2026-40203", "lastModified": "2026-08-28T16:17:57.233", "metrics": {"cvssMetricV31": [{"cvssData": {"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"}, "exploitabilityScore": 2.2, "impactScore": 1.4, "source": "[email protected]", "type": "Secondary"}], "ssvcV203": [{"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "ssvcData": {"id": "CVE-2026-40203", "options": [{"exploitation": "none"}, {"automatable": "no"}, {"technicalImpact": "partial"}], "role": "CISA Coordinator", "timestamp": "2026-08-28T14:56:57.150012Z", "version": "2.0.3"}}]}, "published": "2026-08-28T12:16:28.897", "references": [{"source": "[email protected]", "url": "https://documentation.open-xchange.com/dovecot/security/advisories/csaf/2026/oxdc-adv-2026-0003.json"}], "sourceIdentifier": "[email protected]", "vulnStatus": "Received", "weaknesses": [{"description": [{"lang": "en", "value": "CWE-200"}], "source": "[email protected]", "type": "Secondary"}]}

{"bugzilla": {"description": "dovecot: Dovecot: Information disclosure via IMAP compression side-channel", "id": "2525535", "url": "https://bugzilla.redhat.com/show_bug.cgi?id=2525535"}, "csaw": false, "cvss3": {"cvss3_base_score": "3.7", "cvss3_scoring_vector": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N", "status": "draft"}, "cwe": "CWE-205", "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.", "A flaw was found in dovecot where, when IMAP compression is enabled, the system reuses the same compression state across responses within a session. This allows a remote attacker, who can send mail to a user and monitor the sizes of their IMAP traffic, to potentially deduce the content of small messages. By observing response sizes, an attacker could confirm if a secret message body matches a guessed text, leading to information disclosure."], "mitigation": {"lang": "en:us", "value": "To mitigate this issue, disable IMAP compression in the Dovecot configuration. This typically involves setting `imap_compression = no` in the relevant Dovecot configuration file. After making this change, restart the Dovecot service for the mitigation to take effect. Restarting the service may temporarily interrupt IMAP access for users."}, "name": "CVE-2026-40203", "package_state": [{"cpe": "cpe:/o:redhat:enterprise_linux:10", "fix_state": "Fix deferred", "package_name": "dovecot", "product_name": "Red Hat Enterprise Linux 10"}, {"cpe": "cpe:/o:redhat:enterprise_linux:6", "fix_state": "Out of support scope", "package_name": "dovecot", "product_name": "Red Hat Enterprise Linux 6"}, {"cpe": "cpe:/o:redhat:enterprise_linux:7", "fix_state": "Fix deferred", "package_name": "dovecot", "product_name": "Red Hat Enterprise Linux 7"}, {"cpe": "cpe:/o:redhat:enterprise_linux:8", "fix_state": "Fix deferred", "package_name": "dovecot", "product_name": "Red Hat Enterprise Linux 8"}, {"cpe": "cpe:/o:redhat:enterprise_linux:9", "fix_state": "Fix deferred", "package_name": "dovecot", "product_name": "Red Hat Enterprise Linux 9"}], "public_date": "2026-08-28T10:12:22Z", "references": ["https://www.cve.org/CVERecord?id=CVE-2026-40203\nhttps://nvd.nist.gov/vuln/detail/CVE-2026-40203\nhttps://documentation.open-xchange.com/dovecot/security/advisories/csaf/2026/oxdc-adv-2026-0003.json"], "threat_severity": "Low"}

{"affected": [{"configurations": [{"platform": null, "status": "affected", "versions": {"scheme": "semver", "value": "[2.3.0,2.4.5)"}}], "enrichment": {"confidence": 100.0, "confidence_source": "manual", "scores": [{"score": 100.0, "source": "manual"}]}, "original": {"product": "OX Dovecot CE", "source": "cna", "vendor": "Open-Xchange GmbH"}, "product": "ox_dovecot_ce", "vendor": "open-xchange"}, {"configurations": [{"platform": null, "status": "affected", "versions": {"scheme": "semver", "value": "[2.3.0,2.3.22.2)"}}, {"platform": null, "status": "affected", "versions": {"scheme": "semver", "value": "[3.0.0,3.0.7)"}}, {"platform": null, "status": "affected", "versions": {"scheme": "semver", "value": "[3.1.0,3.1.6)"}}], "enrichment": {"confidence": 95.0, "confidence_source": "inferred", "scores": [{"score": 95.0, "source": "inferred"}, {"score": 100.0, "source": "matching"}]}, "original": {"product": "OX Dovecot Pro", "source": "cna", "vendor": "Open-Xchange GmbH"}, "product": "ox_dovecot_pro", "vendor": "open-xchange"}], "created": "2026-08-28T13:45:17.302752+00:00", "updated": "2026-09-01T14:45:04.123459+00:00", "vendors": ["open-xchange", "open-xchange$PRODUCT$ox_dovecot_ce", "open-xchange$PRODUCT$ox_dovecot_pro"]}