CVE-2026-29140

{"dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": {"cveId": "CVE-2026-29140", "assignerOrgId": "455daabc-a392-441d-aa46-37d35189897c", "state": "PUBLISHED", "assignerShortName": "NCSC.ch", "dateReserved": "2026-03-04T09:08:07.342Z", "datePublished": "2026-04-02T08:27:52.154Z", "dateUpdated": "2026-04-02T14:48:53.216Z"}, "containers": {"cna": {"providerMetadata": {"orgId": "455daabc-a392-441d-aa46-37d35189897c", "shortName": "NCSC.ch", "dateUpdated": "2026-04-02T08:27:52.154Z"}, "title": "S/MIME Signature Additional Certificate", "problemTypes": [{"descriptions": [{"lang": "en", "cweId": "CWE-295", "description": "CWE-295 Improper Certificate Validation", "type": "CWE"}]}], "impacts": [{"capecId": "CAPEC-216", "descriptions": [{"lang": "en", "value": "CAPEC-216 Communication Channel Manipulation"}]}], "affected": [{"vendor": "SEPPmail", "product": "Secure Email Gateway", "versions": [{"status": "affected", "version": "0", "lessThan": "15.0.3", "versionType": "custom"}], "defaultStatus": "unaffected"}], "cpeApplicability": [{"operator": "OR", "nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:a:seppmail:seppmail_secure_email_gateway:*:*:*:*:*:*:*:*", "versionStartIncluding": "0", "versionEndExcluding": "15.0.3"}]}]}], "descriptions": [{"lang": "en", "value": "SEPPmail Secure Email Gateway before version 15.0.3 allows an attacker to cause attacker-controlled certificates to be used for future encryption to a victim by adding the certificates to S/MIME signatures.", "supportingMedia": [{"type": "text/html", "base64": false, "value": "SEPPmail Secure Email Gateway before version 15.0.3 allows an attacker to cause attacker-controlled certificates to be used for future encryption to a victim by adding the certificates to S/MIME signatures."}]}], "references": [{"url": "https://downloads.seppmail.com/extrelnotes/150/ERN15.0.html#seppmail-vulnerability-disclosure-1503", "tags": ["release-notes"]}], "metrics": [{"format": "CVSS", "scenarios": [{"lang": "en", "value": "GENERAL"}], "cvssV4_0": {"attackVector": "NETWORK", "attackComplexity": "LOW", "attackRequirements": "NONE", "privilegesRequired": "NONE", "userInteraction": "NONE", "vulnConfidentialityImpact": "NONE", "subConfidentialityImpact": "HIGH", "vulnIntegrityImpact": "LOW", "subIntegrityImpact": "NONE", "vulnAvailabilityImpact": "NONE", "subAvailabilityImpact": "NONE", "exploitMaturity": "NOT_DEFINED", "Safety": "NOT_DEFINED", "Automatable": "NOT_DEFINED", "Recovery": "NOT_DEFINED", "valueDensity": "NOT_DEFINED", "vulnerabilityResponseEffort": "NOT_DEFINED", "providerUrgency": "NOT_DEFINED", "version": "4.0", "baseSeverity": "HIGH", "baseScore": 7.7, "vectorString": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:H/SI:N/SA:N"}}], "timeline": [{"time": "2025-10-31T14:22:00.000Z", "lang": "en", "value": "Vulnerability disclosed to SEPPmail"}, {"time": "2026-03-03T00:00:00.000Z", "lang": "en", "value": "Version 15.0.3 released"}], "credits": [{"lang": "en", "value": "Andris Suter-D\u00f6rig", "type": "finder"}, {"lang": "en", "value": "Matteo Scarlata", "type": "coordinator"}, {"lang": "en", "value": "Kenny Paterson", "type": "coordinator"}], "source": {"discovery": "EXTERNAL"}, "x_generator": {"engine": "Vulnogram 0.5.0"}}, "adp": [{"metrics": [{"other": {"type": "ssvc", "content": {"timestamp": "2026-04-02T14:48:38.931386Z", "id": "CVE-2026-29140", "options": [{"Exploitation": "none"}, {"Automatable": "yes"}, {"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": "2026-04-02T14:48:53.216Z"}}]}}

{"dataType": "CVE_RECORD", "containers": {"adp": [{"title": "CISA ADP Vulnrichment", "metrics": [{"other": {"type": "ssvc", "content": {"id": "CVE-2026-29140", "role": "CISA Coordinator", "options": [{"Exploitation": "none"}, {"Automatable": "yes"}, {"Technical Impact": "partial"}], "version": "2.0.3", "timestamp": "2026-04-02T14:48:38.931386Z"}}}], "providerMetadata": {"orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "shortName": "CISA-ADP", "dateUpdated": "2026-04-02T14:48:47.837Z"}}], "cna": {"title": "S/MIME Signature Additional Certificate", "source": {"discovery": "EXTERNAL"}, "credits": [{"lang": "en", "type": "finder", "value": "Andris Suter-D\u00f6rig"}, {"lang": "en", "type": "coordinator", "value": "Matteo Scarlata"}, {"lang": "en", "type": "coordinator", "value": "Kenny Paterson"}], "impacts": [{"capecId": "CAPEC-216", "descriptions": [{"lang": "en", "value": "CAPEC-216 Communication Channel Manipulation"}]}], "metrics": [{"format": "CVSS", "cvssV4_0": {"Safety": "NOT_DEFINED", "version": "4.0", "Recovery": "NOT_DEFINED", "baseScore": 7.7, "Automatable": "NOT_DEFINED", "attackVector": "NETWORK", "baseSeverity": "HIGH", "valueDensity": "NOT_DEFINED", "vectorString": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:H/SI:N/SA:N", "exploitMaturity": "NOT_DEFINED", "providerUrgency": "NOT_DEFINED", "userInteraction": "NONE", "attackComplexity": "LOW", "attackRequirements": "NONE", "privilegesRequired": "NONE", "subIntegrityImpact": "NONE", "vulnIntegrityImpact": "LOW", "subAvailabilityImpact": "NONE", "vulnAvailabilityImpact": "NONE", "subConfidentialityImpact": "HIGH", "vulnConfidentialityImpact": "NONE", "vulnerabilityResponseEffort": "NOT_DEFINED"}, "scenarios": [{"lang": "en", "value": "GENERAL"}]}], "affected": [{"vendor": "SEPPmail", "product": "Secure Email Gateway", "versions": [{"status": "affected", "version": "0", "lessThan": "15.0.3", "versionType": "custom"}], "defaultStatus": "unaffected"}], "timeline": [{"lang": "en", "time": "2025-10-31T14:22:00.000Z", "value": "Vulnerability disclosed to SEPPmail"}, {"lang": "en", "time": "2026-03-03T00:00:00.000Z", "value": "Version 15.0.3 released"}], "references": [{"url": "https://downloads.seppmail.com/extrelnotes/150/ERN15.0.html#seppmail-vulnerability-disclosure-1503", "tags": ["release-notes"]}], "x_generator": {"engine": "Vulnogram 0.5.0"}, "descriptions": [{"lang": "en", "value": "SEPPmail Secure Email Gateway before version 15.0.3 allows an attacker to cause attacker-controlled certificates to be used for future encryption to a victim by adding the certificates to S/MIME signatures.", "supportingMedia": [{"type": "text/html", "value": "SEPPmail Secure Email Gateway before version 15.0.3 allows an attacker to cause attacker-controlled certificates to be used for future encryption to a victim by adding the certificates to S/MIME signatures.", "base64": false}]}], "problemTypes": [{"descriptions": [{"lang": "en", "type": "CWE", "cweId": "CWE-295", "description": "CWE-295 Improper Certificate Validation"}]}], "cpeApplicability": [{"nodes": [{"negate": false, "cpeMatch": [{"criteria": "cpe:2.3:a:seppmail:seppmail_secure_email_gateway:*:*:*:*:*:*:*:*", "vulnerable": true, "versionEndExcluding": "15.0.3", "versionStartIncluding": "0"}], "operator": "OR"}], "operator": "OR"}], "providerMetadata": {"orgId": "455daabc-a392-441d-aa46-37d35189897c", "shortName": "NCSC.ch", "dateUpdated": "2026-04-02T08:27:52.154Z"}}}, "cveMetadata": {"cveId": "CVE-2026-29140", "state": "PUBLISHED", "dateUpdated": "2026-04-02T14:48:53.216Z", "dateReserved": "2026-03-04T09:08:07.342Z", "assignerOrgId": "455daabc-a392-441d-aa46-37d35189897c", "datePublished": "2026-04-02T08:27:52.154Z", "assignerShortName": "NCSC.ch"}, "dataVersion": "5.2"}

{"affected": [{"affectedData": [{"defaultStatus": "unaffected", "product": "Secure Email Gateway", "vendor": "SEPPmail", "versions": [{"lessThan": "15.0.3", "status": "affected", "version": "0", "versionType": "custom"}]}], "source": "vulnerability@ncsc.ch"}], "configurations": [{"nodes": [{"cpeMatch": [{"criteria": "cpe:2.3:a:seppmail:secure_email_gateway:*:*:*:*:*:*:*:*", "matchCriteriaId": "E3729650-81CA-4311-94BF-14A7A191F8D1", "versionEndExcluding": "15.0.3", "vulnerable": true}], "negate": false, "operator": "OR"}]}], "cveTags": [], "descriptions": [{"lang": "en", "value": "SEPPmail Secure Email Gateway before version 15.0.3 allows an attacker to cause attacker-controlled certificates to be used for future encryption to a victim by adding the certificates to S/MIME signatures."}, {"lang": "es", "value": "SEPPmail Secure Email Gateway antes de la versi\u00f3n 15.0.3 permite a un atacante provocar que certificados controlados por el atacante sean utilizados para futuro cifrado a una v\u00edctima, a\u00f1adiendo los certificados a las firmas S/MIME."}], "id": "CVE-2026-29140", "lastModified": "2026-10-26T21:10:00.170", "metrics": {"cvssMetricV31": [{"cvssData": {"attackComplexity": "LOW", "attackVector": "NETWORK", "availabilityImpact": "NONE", "baseScore": 5.3, "baseSeverity": "MEDIUM", "confidentialityImpact": "NONE", "integrityImpact": "LOW", "privilegesRequired": "NONE", "scope": "UNCHANGED", "userInteraction": "NONE", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N", "version": "3.1"}, "exploitabilityScore": 3.9, "impactScore": 1.4, "source": "nvd@nist.gov", "type": "Primary"}], "cvssMetricV40": [{"cvssData": {"Automatable": "NOT_DEFINED", "Recovery": "NOT_DEFINED", "Safety": "NOT_DEFINED", "attackComplexity": "LOW", "attackRequirements": "NONE", "attackVector": "NETWORK", "availabilityRequirement": "NOT_DEFINED", "baseScore": 7.7, "baseSeverity": "HIGH", "confidentialityRequirement": "NOT_DEFINED", "exploitMaturity": "NOT_DEFINED", "integrityRequirement": "NOT_DEFINED", "modifiedAttackComplexity": "NOT_DEFINED", "modifiedAttackRequirements": "NOT_DEFINED", "modifiedAttackVector": "NOT_DEFINED", "modifiedPrivilegesRequired": "NOT_DEFINED", "modifiedSubAvailabilityImpact": "NOT_DEFINED", "modifiedSubConfidentialityImpact": "NOT_DEFINED", "modifiedSubIntegrityImpact": "NOT_DEFINED", "modifiedUserInteraction": "NOT_DEFINED", "modifiedVulnAvailabilityImpact": "NOT_DEFINED", "modifiedVulnConfidentialityImpact": "NOT_DEFINED", "modifiedVulnIntegrityImpact": "NOT_DEFINED", "privilegesRequired": "NONE", "providerUrgency": "NOT_DEFINED", "subAvailabilityImpact": "NONE", "subConfidentialityImpact": "HIGH", "subIntegrityImpact": "NONE", "userInteraction": "NONE", "valueDensity": "NOT_DEFINED", "vectorString": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:H/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X", "version": "4.0", "vulnAvailabilityImpact": "NONE", "vulnConfidentialityImpact": "NONE", "vulnIntegrityImpact": "LOW", "vulnerabilityResponseEffort": "NOT_DEFINED"}, "source": "vulnerability@ncsc.ch", "type": "Secondary"}], "ssvcV203": [{"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "ssvcData": {"id": "CVE-2026-29140", "options": [{"exploitation": "none"}, {"automatable": "yes"}, {"technicalImpact": "partial"}], "role": "CISA Coordinator", "timestamp": "2026-04-02T14:48:38.931386Z", "version": "2.0.3"}}]}, "published": "2026-04-02T09:16:22.623", "references": [{"source": "vulnerability@ncsc.ch", "tags": ["Release Notes"], "url": "https://downloads.seppmail.com/extrelnotes/150/ERN15.0.html#seppmail-vulnerability-disclosure-1503"}], "sourceIdentifier": "vulnerability@ncsc.ch", "vulnStatus": "Analyzed", "weaknesses": [{"description": [{"lang": "en", "value": "CWE-295"}], "source": "vulnerability@ncsc.ch", "type": "Secondary"}]}

{}

{"affected": [{"configurations": [{"platform": null, "status": "affected", "versions": {"scheme": "semver", "value": "[0,15.0.3)"}}], "enrichment": {"confidence": 87.0, "confidence_source": "matching", "scores": [{"score": 95.0, "source": "inferred"}, {"score": 87.0, "source": "matching"}]}, "original": {"product": "Secure Email Gateway", "source": "cna", "vendor": "SEPPmail"}, "product": "seppmail_secure_email_gateway", "vendor": "seppmail"}], "analysis": {"en": {"generated_at": "2026-04-02T09:50:24.904759+00:00", "value": {"mitigation_remediation": ["Upgrade SEPPmail Secure Email Gateway to version\u202f15.0.3 or newer, following the vendor\u2019s release notes.", "If an immediate upgrade is not possible, configure mail\u2011gateway rules to reject S/MIME signatures that contain certificates not issued by a trusted CA or that are not listed in the gateway\u2019s client\u2011store.", "Verify the upgrade by sending test encrypted mail and checking that the gateway uses certificates from the approved trust store.", "Monitor mail logs for abnormal certificate usage and keep the system patched as new guidance becomes available."], "summary": {"action": "Immediate Patch", "impact": "Adversary-controlled certificates used for future email encryption"}, "threat_synthesis": {"affected_systems": "All deployments of SEPPmail Secure Email Gateway running any version earlier than 15.0.3 are affected. Because the vulnerability is tied to the version number, administrators should verify their current release and ensure it meets or exceeds the 15.0.3 baseline. No specific patch level is listed beyond the fixed version; any release prior to 15.0.3 remains vulnerable.", "description_and_impact": "SEPPmail Secure Email Gateway versions before 15.0.3 contain a flaw that lets an attacker embed a forged certificate into an S/MIME signature. When the gateway subsequently encrypts communications with a victim, it selects and uses the attacker\u2011controlled certificate. This capability can allow the attacker to decrypt, alter, or fabricate mail sent by the gateway, effectively turning the encryption mechanism into a vector for data disclosure and spoofing. The weakness follows the certificate\u2011validation error described in CWE\u2011295.", "risk_and_exploitability": "The CVSS v3.1 score of 7.7 indicates a high severity that can compromise confidentiality and integrity. EPSS data is unavailable, but the lack of a CISA KEV listing suggests no publicly known exploit at the time of disclosure. The attack can be performed remotely by any actor able to send S/MIME\u2011signed messages to the affected gateway, and it does not require elevated privileges. The likely attack vector is inferred to be remote via crafted S/MIME signatures, enabling the attacker to influence the encryption process for future mail traffic."}}}}, "created": "2026-04-02T20:15:34.094605+00:00", "updated": "2026-04-02T20:22:09.579176+00:00", "vendors": ["seppmail", "seppmail$PRODUCT$seppmail_secure_email_gateway"]}