{"id":"CVE-2026-107566","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.","modified":"2026-10-20T02:46:33.983484200Z","published":"2026-10-19T15:34:27.491Z","database_specific":{"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/107xxx/CVE-2026-107566.json","cna_assigner":"GitLab","cwe_ids":["CWE-862"]},"references":[{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/107xxx/CVE-2026-107566.json"},{"type":"PACKAGE","url":"https://gitlab.com/hmailserver/hmailserver"},{"type":"WEB","url":"https://gitlab.com/hmailserver/hmailserver/-/releases/v6.3.7"},{"type":"WEB","url":"https://gitlab.com/hmailserver/hmailserver/-/work_items/83"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-107566"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://gitlab.com/hmailserver/hmailserver","events":[{"introduced":"e4b7163189ac6ce365bb954cf3e264e2e3105a18"},{"last_affected":"e3c448aa66fc310b74d076884d54fae951296915"}],"database_specific":{"extracted_events":[{"introduced":"6.0.0"},{"last_affected":"6.3.6"}],"source":"AFFECTED_FIELD"}}],"versions":["v6.3.6","v6.3.5","v6.3.4","v6.3.3","v6.3.2","build-inputs-1","v6.3.1","v6.3.0","v6.2.28","v6.2.27","v6.2.26","v6.2.25","v6.2.24","v6.2.23-alpha2","v6.2.23-alpha1","v6.2.22-pre6","v6.2.22-pre5","v6.2.22-pre4","v6.2.22-pre3","v6.2.22-pre2","v6.2.22-pre1","v6.2.21","v6.2.20","v6.2.19","v6.2.18","v6.2.17","v6.2.16","v6.2.15","v6.2.14","v6.2.13","v6.2.12","v6.2.11","v6.2.10","v6.2.9","v6.2.8","v6.2.7","v6.2.6","v6.2.5","v6.2.4","v6.2.3","v6.2.2","v6.2.1","v6.2.0","v6.1.0","v6.0.0-B4","v6.0.0-B3","v6.0.0"],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-107566.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N"}]}