{
  "affected": [
    {
      "ranges": [
        {
          "database_specific": {
            "extracted_events": [
              {
                "introduced": "6.0.0"
              },
              {
                "fixed": "6.3.6"
              },
              {
                "fixed": "6.3.5"
              }
            ],
            "source": [
              "AFFECTED_FIELD",
              "DESCRIPTION"
            ]
          },
          "events": [
            {
              "introduced": "e4b7163189ac6ce365bb954cf3e264e2e3105a18"
            },
            {
              "fixed": "e3c448aa66fc310b74d076884d54fae951296915"
            }
          ],
          "repo": "https://gitlab.com/hmailserver/hmailserver",
          "type": "GIT"
        }
      ]
    }
  ],
  "database_specific": {
    "cna_assigner": "GitLab",
    "cwe_ids": [
      "CWE-407"
    ],
    "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/107xxx/CVE-2026-107576.json"
  },
  "details": "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.",
  "id": "CVE-2026-107576",
  "modified": "2026-10-10T02:30:46.394227839Z",
  "published": "2026-10-08T11:46:56.083Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://gitlab.com/hmailserver/hmailserver/-/releases/v6.3.6"
    },
    {
      "type": "WEB",
      "url": "https://gitlab.com/hmailserver/hmailserver/-/work_items/73"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/107xxx/CVE-2026-107576.json"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-107576"
    },
    {
      "type": "PACKAGE",
      "url": "https://gitlab.com/hmailserver/hmailserver"
    }
  ],
  "schema_version": "1.9.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
      "type": "CVSS_V3"
    }
  ],
  "summary": "Inefficient Algorithmic Complexity in hMailServer"
}