{
  "affected": [
    {
      "ranges": [
        {
          "database_specific": {
            "extracted_events": [
              {
                "introduced": "6.0.0"
              },
              {
                "last_affected": "6.3.6"
              }
            ],
            "source": "AFFECTED_FIELD"
          },
          "events": [
            {
              "introduced": "e4b7163189ac6ce365bb954cf3e264e2e3105a18"
            },
            {
              "last_affected": "e3c448aa66fc310b74d076884d54fae951296915"
            }
          ],
          "repo": "https://gitlab.com/hmailserver/hmailserver",
          "type": "GIT"
        }
      ]
    }
  ],
  "database_specific": {
    "cna_assigner": "GitLab",
    "cwe_ids": [
      "CWE-862"
    ],
    "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/107xxx/CVE-2026-107566.json"
  },
  "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.",
  "id": "CVE-2026-107566",
  "modified": "2026-10-20T02:30:21.468538978Z",
  "published": "2026-10-19T15:34:27.491Z",
  "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"
    }
  ],
  "schema_version": "1.9.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "Missing Authorization in hMailServer"
}