{"schema":"threatline.record/2","record":{"id":"CVE-2026-107569","aliases":[],"summary":"Unchecked Input for Loop Condition in hMailServer","details":"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.","categories":["Unclassified"],"product":"hMailServer","vendor":"Progressive Robot Ltd","ecosystem":null,"affected_ranges":[{"source":"CVE List","source_url":"https://www.cve.org/CVERecord?id=CVE-2026-107569","source_modified_at":"2026-10-20T19:27:26.604Z","fetched_at":"2026-10-23T18:45:31.882637Z","product":"hMailServer","vendor":"Progressive Robot Ltd","versions":[{"version":"6.0.0","status":"affected","lessThanOrEqual":"6.3.6","versionType":"semver"}],"defaultStatus":"unaffected"}],"fixed_versions":[],"cvss":7.5,"severity":"High","kev":{"listed":false},"epss":{"probability":0.00372,"percentile":0.29961,"score_date":"2026-10-23"},"published_at":"2026-10-19T15:34:37.492Z","modified_at":"2026-10-20T19:27:26.604Z","provenance":[{"source":"CVE List","url":"https://www.cve.org/CVERecord?id=CVE-2026-107569","fetched_at":"2026-10-23T18:45:31.882637Z","source_modified_at":"2026-10-20T19:27:26.604Z"},{"source":"EPSS","url":"https://api.first.org/data/v1/epss?cve=CVE-2026-107569","fetched_at":"2026-10-23T18:42:43.628194Z","source_modified_at":"2026-10-23"}],"sources":["CVE List","EPSS"],"references":[{"source":"CVE List","url":"https://gitlab.com/hmailserver/hmailserver/-/work_items/81"},{"source":"CVE List","url":"https://gitlab.com/hmailserver/hmailserver/-/releases/v6.3.7"}],"locations":[],"motoko_assessment":{"status":"requires_architecture_review","automatic_remediation":false},"cve_state":"PUBLISHED","cvss_source":"CVE List","ssvc":{"exploitation":"none","automatable":"yes","technical_impact":"partial","assessed_at":"2026-10-20T19:27:14.386515Z"},"classification":{"method":"product-first software-layer rules","rules_version":"2.1","matched_on":null,"confidence":"unknown","reviewed":false},"change_timestamp":"2026-10-20T19:27:26.604Z","content_hash":"efad1eecd18247c52fe900287fa043cc60ef8742375a1abe58216967111bca98"}}