{"schema":"threatline.record/2","record":{"id":"CVE-2026-107576","aliases":[],"summary":"Inefficient Algorithmic Complexity in hMailServer","details":"Inefficient algorithmic complexity in the inbound DKIM and ARC signature verification of Progressive Robot hMailServer 6.0.0 through 6.3.5 allows a remote unauthenticated attacker to make the mail services unavailable by sending a message. Building the canonical header and choosing the header fields named in a signature's h= tag took time growing with the square of the message's header: the 'simple' canonicalisation prepended each continuation line of a folded field to the lines already gathered, and both canonicalisations searched the gathered fields from the bottom for each h= name and erased the match from the middle of the list. A message whose header holds very many fields, or a field folded over very many lines, with a DKIM-Signature the attacker signs for a domain they control, keeps a worker thread busy for tens of seconds per signature; up to ten signatures are evaluated per message by each of the DKIM and DMARC tests, on the threads that serve delivery and SMTP.","categories":["Unclassified"],"product":"hMailServer","vendor":"Progressive Robot Ltd","ecosystem":null,"affected_ranges":[{"source":"CVE List","source_url":"https://www.cve.org/CVERecord?id=CVE-2026-107576","source_modified_at":"2026-10-08T14:15:09.064Z","fetched_at":"2026-10-23T18:48:36.087640Z","product":"hMailServer","vendor":"Progressive Robot Ltd","versions":[{"version":"6.0.0","status":"affected","lessThan":"6.3.6","versionType":"semver"}],"defaultStatus":"unaffected"}],"fixed_versions":[{"source":"CVE List","source_url":"https://www.cve.org/CVERecord?id=CVE-2026-107576","source_modified_at":"2026-10-08T14:15:09.064Z","fetched_at":"2026-10-23T18:48:36.087640Z","package":{"name":"hMailServer","ecosystem":null},"version":"6.3.6","basis":"first unaffected version stated in the CVE record"}],"cvss":7.5,"severity":"High","kev":{"listed":false},"epss":{"probability":0.00428,"percentile":0.35999,"score_date":"2026-10-23"},"published_at":"2026-10-08T11:46:56.083Z","modified_at":"2026-10-08T14:15:09.064Z","provenance":[{"source":"CVE List","url":"https://www.cve.org/CVERecord?id=CVE-2026-107576","fetched_at":"2026-10-23T18:48:36.087640Z","source_modified_at":"2026-10-08T14:15:09.064Z"},{"source":"EPSS","url":"https://api.first.org/data/v1/epss?cve=CVE-2026-107576","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/73"},{"source":"CVE List","url":"https://gitlab.com/hmailserver/hmailserver/-/releases/v6.3.6"}],"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":"2026-10-08T14:14:51.935522Z"},"classification":{"method":"product-first software-layer rules","rules_version":"2.1","matched_on":null,"confidence":"unknown","reviewed":false},"change_timestamp":"2026-10-08T14:15:09.064Z","content_hash":"a4d4f689abb85a6ad3c4191d7b88526a0cb428356b1889aef5a40ee0b9e464f9"}}