Inefficient Algorithmic Complexity in hMailServer

{
  "id": "ef76f07709f3b5e20f47ae42749cedefdc677ce7b25eb0f95d8895c5f17d0d09",
  "url": "https://osv.dev/vulnerability/CVE-2026-107575",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "Inefficient Algorithmic Complexity in hMailServer",
    "summary": "Inefficient algorithmic complexity in the SPF macro expansion of Progressive Robot hMailServer 6.3.4 and 6.3.5 allows a remote unauthenticated attacker to consume worker-thread time by publishing a crafted SPF record. RFC 7208 section 7.1 requires a name too long to look up to lose whole labels from the left; the server did this by removing one label at a time and copying the rest of the name each time, so the work grew with the square of the expansion. An attacker who publishes an SPF record for a domain they control, with a mechanism whose domain-spec expands through macros to a name far longer than 253 characters, makes the SPF check of a message from that domain take several seconds. The expansion is bounded by SPF's own per-term and per-macro limits, so the loss of availability is partial.",
    "evidence": "osv:CVE-2026-107575",
    "products": [],
    "severity": "medium",
    "structured": {
      "id": "CVE-2026-107575",
      "aliases": [
        "CVE-2026-107575"
      ],
      "metrics": [
        {
          "type": "CVSS_V3",
          "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://gitlab.com/hmailserver/hmailserver",
              "type": "GIT",
              "events": [
                {
                  "introduced": "51e2dbda08d6aa7fcda5a48f1af05221809f78be"
                },
                {
                  "fixed": "e3c448aa66fc310b74d076884d54fae951296915"
                }
              ],
              "database_specific": {
                "extracted_events": [
                  {
                    "range": [
                      {
                        "introduced": "6.3.4"
                      },
                      {
                        "fixed": "6.3.6"
                      }
                    ],
                    "source": "AFFECTED_FIELD",
                    "strategy": "StandardRange"
                  }
                ]
              }
            }
          ],
          "versions": [
            "v6.3.5",
            "v6.3.4"
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-107575.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:33.434920689Z",
      "provider": "osv",
      "references": [
        "https://gitlab.com/hmailserver/hmailserver/-/releases/v6.3.6",
        "https://gitlab.com/hmailserver/hmailserver/-/work_items/74",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/107xxx/CVE-2026-107575.json",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-107575",
        "https://gitlab.com/hmailserver/hmailserver"
      ],
      "provider_metadata": {
        "cwe_ids": [
          "CWE-407"
        ],
        "cna_assigner": "GitLab",
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/107xxx/CVE-2026-107575.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-107575",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 500448,
  "published_at": "2026-10-08T11:46:46.082+00:00"
}