{"schema":"threatline.record/2","record":{"id":"CVE-2026-107566","aliases":[],"summary":"Missing Authorization in hMailServer","details":"Missing authorization in the Sieve editheader action (6.2.22 through 6.3.6) and in the mail-rule Set header value action (6.0.0 through 6.3.6) of Progressive Robot hMailServer allows an authenticated user to make the server send mail as any address, DKIM-signed where the address is at a domain the server signs for. A Sieve script's editheader (addheader/deleteheader) could add or delete any header field except Received and Return-Path, and the server applies a script's header edits before it queues a redirect, so the redirected copy is sent as the script left it. The server signs a message's first delivery pass as the domain named in its From header wherever it signs DKIM for that domain and the message carries no signature of it. A script could therefore delete and re-add From - another account's address, or anyone's at a hosted domain - and redirect, so the server sent the message in that name and, for a hosted domain, signed it with that domain's DKIM key, a forgery aligned to pass the domain's DMARC; or, where another sender's domain is one the server signs for, delete the DKIM-Signature that sender's message arrived with, alter a field, and redirect, so the server re-signed the altered message as that sender's domain. editheader placed no restriction on From, Sender, Resent-From, Resent-Sender or DKIM-Signature. The editheader action was introduced in 6.2.22. In the mail-rule engine, a domain's or an account's rule's Set header value action could likewise set From, Sender, Resent-From, Resent-Sender or DKIM-Signature ahead of a forward or a copy, whoever the rule belonged to, so that an account acting on its own rules over COM, a domain administrator, or an API key confined to a domain (over the REST API from 6.3.4) could have the server forward or copy a message in the name of any address, signed, where that address is at a domain the server hosts with DKIM signing enabled, with that domain's key.","categories":["Unclassified"],"product":"hMailServer","vendor":"Progressive Robot Ltd","ecosystem":null,"affected_ranges":[{"source":"CVE List","source_url":"https://www.cve.org/CVERecord?id=CVE-2026-107566","source_modified_at":"2026-10-20T19:25:48.560Z","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":6.5,"severity":"Medium","kev":{"listed":false},"epss":{"probability":0.00181,"percentile":0.07313,"score_date":"2026-10-23"},"published_at":"2026-10-19T15:34:27.491Z","modified_at":"2026-10-20T19:25:48.560Z","provenance":[{"source":"CVE List","url":"https://www.cve.org/CVERecord?id=CVE-2026-107566","fetched_at":"2026-10-23T18:45:31.882637Z","source_modified_at":"2026-10-20T19:25:48.560Z"},{"source":"EPSS","url":"https://api.first.org/data/v1/epss?cve=CVE-2026-107566","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/83"},{"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":"no","technical_impact":"partial","assessed_at":"2026-10-20T19:25:38.300931Z"},"classification":{"method":"product-first software-layer rules","rules_version":"2.1","matched_on":null,"confidence":"unknown","reviewed":false},"change_timestamp":"2026-10-20T19:25:48.560Z","content_hash":"f066f088da9522cdb269ce176013549489ef8b7db03439ff5937aadefcaebfbb"}}