{"id":"CVE-2026-103649","revision":null,"records":[{"revision":"d29b8ab7ad87434699d6be9eafe203a2","observedAt":"2026-10-23T15:48:27.903+00:00","statement":{"source":"cve-program","id":"CVE-2026-103649","aliases":[],"title":"Synchronous Access of Remote Resource without Timeout in hMailServer","description":"Missing network timeouts in the Linux builds of Progressive Robot hMailServer 6.3.0 through 6.3.5 allow a remote attacker to hold server threads indefinitely and so stop outbound mail delivery (denial of service). The server set its socket timeouts in the form Windows takes, which Linux refuses, and its HTTPS clients read without a deadline, so a peer that accepts a connection and then sends nothing held the waiting thread for as long as the connection stayed open. The MTA-STS policy fetch, enabled by default, is made during outbound delivery to mta-sts.<recipient domain>, so anyone who can make the server deliver mail to a domain they control - for example as the envelope sender of a message that bounces - can hold delivery threads until outbound delivery stops. The same flaw affects the DANE TLSA query, the OAuth2 token request, the ACME client, and the ManageSieve and metrics listeners, which a silent client stops from serving anyone else. Windows builds are not affected.","state":0,"publishedAt":"2026-10-08T10:53:00.63+00:00","modifiedAt":"2026-10-08T14:24:21.363+00:00","affected":[{"ecosystem":"Vendor product","name":"hMailServer","ranges":[],"versions":[],"rawVersionEvidence":"{\n                    \"vendor\": \"Progressive Robot Ltd\",\n                    \"product\": \"hMailServer\",\n                    \"repo\": \"https://gitlab.com/hmailserver/hmailserver\",\n                    \"versions\": [\n                        {\n                            \"version\": \"6.3.0\",\n                            \"status\": \"affected\",\n                            \"lessThan\": \"6.3.6\",\n                            \"versionType\": \"semver\"\n                        }\n                    ],\n                    \"defaultStatus\": \"unaffected\"\n                }"}],"metrics":[{"system":"CVSS 3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","score":7.5,"severity":"HIGH"}],"references":["https://gitlab.com/hmailserver/hmailserver/-/work_items/53","https://gitlab.com/hmailserver/hmailserver/-/releases/v6.3.6"],"sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-103649","license":"CVE Program Terms of Use","key":"cve-program:CVE-2026-103649","identifiers":["CVE-2026-103649"]},"retained":false,"historicalAffected":[]}],"coverage":[{"source":"cisa-kev:global","scope":"Complete CISA KEV catalog; all vendors. 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Not a global EUVD catalog. Successful not-found lookups count as checked; they do not imply withdrawal or safety. No reader inventory is sent.","generation":"enrichment-a5bcdf6ab6d94076983501bc0e56dd96","complete":false,"records":13754,"lastAttemptAt":"2026-11-11T08:39:48.5063796+00:00","lastSuccessAt":"2026-11-11T08:39:48.502+00:00","error":"16 identifier lookups failed; latest failures include HTTP 403. Other identifiers were checked independently.","lastVerifiedAt":"2026-11-11T08:39:48.502+00:00","snapshotPublishedAt":null,"importing":false,"stagedRecords":0,"checkedIdentifiers":13770,"expectedIdentifiers":13808,"failedIdentifiers":16},{"source":"first-epss:nuget","scope":"FIRST EPSS for explicit CVE aliases in the collected public NuGet archive. Not a global EPSS backfill.","generation":"2026-11-11T08:27:47.0671487+00:00","complete":true,"records":1097,"lastAttemptAt":"2026-11-11T08:27:47.0671487+00:00","lastSuccessAt":"2026-11-11T08:27:47.3858436+00:00","error":null,"lastVerifiedAt":"2026-11-11T08:27:47.3858438+00:00","snapshotPublishedAt":null,"importing":false,"stagedRecords":0,"checkedIdentifiers":null,"expectedIdentifiers":null,"failedIdentifiers":null},{"source":"nvd","scope":"Rolling NVD lookups of CVE aliases in current public OSV archives; 500 identifiers per refresh, rechecked after 48 hours. Not a global NVD catalog. Successful not-found lookups count as checked; they do not imply withdrawal or safety. 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