{"id":"CVE-2026-107566","aliases":["EUVD-2026-104408","GHSA-87p7-4v38-33c9"],"status":"published","title":"Missing Authorization in hMailServer","description":"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.","severity":{"version":"3.1","score":6.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N","level":"medium","assessor":"cna","from":"cve"},"epss":{"day":"2026-11-11","score":0.00181,"percentile":0.07792,"model":"v2026.06.15"},"facts":{"in_kev":false,"known_exploited":false,"public_exploit":false,"fix_available":false},"cwes":["CWE-862"],"published":"2026-10-19T15:34:27Z","modified":"2026-10-28T02:30:50Z","products":[{"vendor":"progressive robot ltd","product":"hmailserver"}],"references":[{"url":"https://gitlab.com/hmailserver/hmailserver/-/work_items/83","tags":["web"]},{"url":"https://gitlab.com/hmailserver/hmailserver/-/releases/v6.3.7","tags":["web"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-107566","tags":["advisory"]},{"url":"https://github.com/advisories/GHSA-87p7-4v38-33c9"},{"url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/107xxx/CVE-2026-107566.json","tags":["advisory"]},{"url":"https://gitlab.com/hmailserver/hmailserver","tags":["package"]}],"sources":{"cve":[{"id":"CVE-2026-107566","title":"Missing Authorization in hMailServer","description":"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.","status":"published","published":"2026-10-19T15:34:27.491Z","modified":"2026-10-20T19:25:48.56Z","cvss":[{"version":"3.1","score":6.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N","level":"medium","assessor":"cna"}],"cwes":["CWE-862"],"updated_at":"2026-11-02T13:45:14.072357Z"}],"euvd":[{"id":"EUVD-2026-104408","description":"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.","status":"published","published":"2026-10-19T15:34:27Z","modified":"2026-10-20T19:25:48Z","cvss":[{"version":"3.1","score":6.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N","level":"medium"}],"updated_at":"2026-11-02T16:59:42.590373Z"}],"ghsa":[{"id":"GHSA-87p7-4v38-33c9","title":"Missing authorization in the Sieve editheader action (6.2.22 through 6.3.6) and in the mail-rule...","description":"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.","status":"published","published":"2026-10-19T18:32:11Z","modified":"2026-10-19T18:32:15Z","cvss":[{"version":"3.1","score":6.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N","level":"medium"}],"cwes":["CWE-862"],"updated_at":"2026-11-02T15:13:57.629988Z"}],"nvd":[{"id":"CVE-2026-107566","description":"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.","status":"published","published":"2026-10-19T16:17:01.46Z","modified":"2026-10-20T20:17:13.577Z","cvss":[{"version":"3.1","score":6.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N","level":"medium","assessor":"secondary"}],"cwes":["CWE-862"],"updated_at":"2026-11-02T14:13:00.83844Z"}],"osv":[{"id":"CVE-2026-107566","title":"Missing Authorization in hMailServer","description":"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.","status":"published","published":"2026-10-19T15:34:27.491Z","modified":"2026-10-28T02:30:50.615149359Z","cvss":[{"version":"3.1","score":6.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N","level":"medium"}],"cwes":["CWE-862"],"updated_at":"2026-11-02T15:44:54.933106Z"}]}}