{"identifier":"CVE-2026-107569","cve":{"id":"CVE-2026-107569","description":"Unchecked input for a loop condition in Progressive Robot hMailServer 6.0.0 through 6.3.6 allows a remote unauthenticated attacker to stop the server carrying mail. The server bounds the mail it generates in response to a message - a rule forward, reply or copy, an account forward, a Sieve redirect, vacation or notify, a bounce, an out-of-office reply - by a counter it carries in the message's X-hMailServer-LoopCount header, and makes no more once the counter reaches the configured rule loop limit (5 by default); that is what ends a forwarding or auto-reply cycle in a bounded number of hops. X-hMailServer-LoopCount is an ordinary header that is not stripped from mail arriving from outside, and the server read it with a signed conversion and no validation, so a count below zero passed every test against the limit: a sender who sets X-hMailServer-LoopCount to a negative value, or on the Linux builds to a value above the 32-bit signed range that the conversion wraps to a negative one, lifts the bound, and a message that enters a generated-mail cycle then loops up to about two thousand million times, each hop a queued message and a delivery, filling the queue and disk and stopping mail service. The Sieve notify action (from 6.2.22) consulted no limit at all, and its increment of the count could overflow a signed integer; and an account could reset the counter on its own mail through a Sieve editheader of the header (from 6.2.22) or a rule Set header value action (all versions) ahead of a forward or redirect.","published":"2026-10-19T16:17:01.830000+00:00","modified":"2026-10-20T20:17:13.973000+00:00","status":"Deferred","score":7.5,"severity":"HIGH","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","cvss_version":"3.1","affected":[],"weaknesses":["CWE-606"],"references":[{"url":"https://gitlab.com/hmailserver/hmailserver/-/releases/v6.3.7","source":"cve@gitlab.com"},{"url":"https://gitlab.com/hmailserver/hmailserver/-/work_items/81","source":"cve@gitlab.com"}],"kev":null,"kev_checked":true,"metrics":{"cvssMetricV31":[{"source":"cve@gitlab.com","type":"Secondary","cvssData":{"version":"3.1","vectorString":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","baseScore":7.5,"baseSeverity":"HIGH","attackVector":"NETWORK","attackComplexity":"LOW","privilegesRequired":"NONE","userInteraction":"NONE","scope":"UNCHANGED","confidentialityImpact":"NONE","integrityImpact":"NONE","availabilityImpact":"HIGH"},"exploitabilityScore":3.9,"impactScore":3.6}],"ssvcV203":[{"source":"134c704f-9b21-4f2e-91b3-4a467353bcc0","ssvcData":{"timestamp":"2026-10-20T19:27:14.386515Z","id":"CVE-2026-107569","options":[{"exploitation":"none"},{"automatable":"yes"},{"technicalImpact":"partial"}],"role":"CISA Coordinator","version":"2.0.3"}}]},"configurations":[],"source":"nvd","retrieved_at":"2026-10-28T10:23:45.547354+00:00","exploited":false,"kev_stale":false,"products":[],"priority":{"label":"Assess exposure and vendor guidance","reasons":["No higher-priority signal is available in the current stored evidence."]},"epss":{"probability":0.00372,"percentile":0.31033,"date":"2026-10-28","stale":false},"version_assessment":null},"news":[],"campaigns":[],"domains":[{"domain":"gitlab.com","source_url":"https://gitlab.com/hmailserver/hmailserver/-/releases/v6.3.7","investigate_url":"https://investigate.aeglixmind.com/#gitlab.com"}],"arsenal_url":"https://arsenal.aeglixmind.com/?cve=CVE-2026-107569","catalog_url":"https://cves.aeglixmind.com/cve/CVE-2026-107569","research_url":"https://investigate.aeglixmind.com/research/cve/CVE-2026-107569","coverage":{"news_candidates_checked":0,"campaign_candidates_checked":0,"bounded":false,"notice":"Exact CVE mentions in stored public excerpts and reviewed campaign content only. A mention is not proof of exploitation, attribution or tool suitability. Missing matches do not establish absence."}}