Zammad: S/MIME signature verification allows forged sender impersonation

{
  "id": "932f82ea47729a5311dffd6f51bc955f8d2d80191fd56d5f48e645dc50139474",
  "url": "https://osv.dev/vulnerability/CVE-2026-84465",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "Zammad: S/MIME signature verification allows forged sender impersonation",
    "summary": "Zammad is a web based open source helpdesk/customer support system. Prior to 7.1.2, when Zammad checks the digital signature on an incoming S/MIME-signed email, it does not verify that the signing certificate is genuinely trusted, it only checks whether a certificate with a matching name is already stored in the system. An attacker can create their own certificate using the name of a real, previously trusted sender and use it to send a forged email. Zammad will display that email with the same \"validly signed\" indicator as a genuine message from the real sender, even though the attacker never had access to that sender's actual certificate or private key. This issue is fixed in version 7.1.2.",
    "evidence": "osv:CVE-2026-84465",
    "products": [],
    "severity": "high",
    "structured": {
      "id": "CVE-2026-84465",
      "aliases": [
        "CVE-2026-84465",
        "GHSA-m9ff-hjr3-93h4"
      ],
      "metrics": [
        {
          "type": "CVSS_V4",
          "score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://github.com/zammad/zammad",
              "type": "GIT",
              "events": [
                {
                  "introduced": "0"
                },
                {
                  "fixed": "7195a4a3e3ba9e801b6ad93f191ae423ed573d15"
                },
                {
                  "fixed": "9a07d0b8214ac4e8e10c23fce71d613bd0625524"
                }
              ],
              "database_specific": {
                "extracted_events": [
                  {
                    "range": [
                      {
                        "introduced": "0"
                      },
                      {
                        "fixed": "7.1.2"
                      }
                    ],
                    "source": "AFFECTED_FIELD",
                    "strategy": "StringRangeExpression"
                  },
                  {
                    "range": [
                      {
                        "fixed": "9a07d0b8214ac4e8e10c23fce71d613bd0625524"
                      }
                    ],
                    "source": "REFERENCES_COMMIT"
                  }
                ]
              }
            }
          ],
          "versions": [
            "7.1.1",
            "7.1.0",
            "7.1.0-alpha",
            "7.0.0-alpha",
            "6.6.0-alpha",
            "6.5.0-alpha",
            "6.4.0-alpha",
            "6.3.0-alpha",
            "6.2.0-alpha",
            "6.1.0-alpha",
            "6.0.0-alpha",
            "5.5.0-alpha",
            "5.4.0-alpha",
            "5.3.0-alpha",
            "5.2.0-alpha",
            "3.7.0",
            "1.6.0"
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-84465.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:30.813356530Z",
      "provider": "osv",
      "references": [
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/84xxx/CVE-2026-84465.json",
        "https://github.com/zammad/zammad/security/advisories/GHSA-m9ff-hjr3-93h4",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-84465",
        "https://github.com/zammad/zammad/commit/9a07d0b8214ac4e8e10c23fce71d613bd0625524"
      ],
      "provider_metadata": {
        "cwe_ids": [
          "CWE-290",
          "CWE-295",
          "CWE-347"
        ],
        "cna_assigner": "GitHub_M",
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/84xxx/CVE-2026-84465.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-84465",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 497672,
  "published_at": "2026-09-25T18:19:58.735+00:00"
}