{"id":"CVE-2026-107576","revision":"b7364a072a564201abe0aa1c502f329d","records":[{"revision":"b7364a072a564201abe0aa1c502f329d","observedAt":"2026-10-23T15:48:27.903+00:00","statement":{"source":"cve-program","id":"CVE-2026-107576","aliases":[],"title":"Inefficient Algorithmic Complexity in hMailServer","description":"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.","state":0,"publishedAt":"2026-10-08T11:46:56.083+00:00","modifiedAt":"2026-10-08T14:15:09.064+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\": \"6.0.0\",\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/73","https://gitlab.com/hmailserver/hmailserver/-/releases/v6.3.6"],"sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-107576","license":"CVE Program Terms of Use","key":"cve-program:CVE-2026-107576","identifiers":["CVE-2026-107576"]},"retained":false,"historicalAffected":[]}],"coverage":[]}