issue was discovered in the base64d function in the SMTP listener in Exim before 4

{
  "id": "f01a4a6888be244ceb46a05f45a38fb91b919563470b7edd4e3e8764edd9410c",
  "url": "https://osv.dev/vulnerability/CLEANSTART-2025-AY16629",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "issue was discovered in the base64d function in the SMTP listener in Exim before 4",
    "summary": "Security vulnerability affects the exim package. An issue was discovered in the base64d function in the SMTP listener in Exim before 4.",
    "evidence": "osv:CLEANSTART-2025-AY16629",
    "products": [
      {
        "name": {
          "value": "exim",
          "evidence": "/affected/0/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [
          {
            "value": "4.90.1-r0",
            "evidence": "/affected/0/ranges"
          }
        ],
        "affected_versions": []
      }
    ],
    "severity": "critical",
    "structured": {
      "id": "CLEANSTART-2025-AY16629",
      "aliases": [
        "CLEANSTART-2025-AY16629"
      ],
      "metrics": [
        {
          "type": "CVSS_V3",
          "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "0"
                },
                {
                  "fixed": "4.90.1-r0"
                }
              ]
            }
          ],
          "package": {
            "name": "exim",
            "purl": "pkg:apk/cleanstart/exim",
            "ecosystem": "CleanStart"
          },
          "database_specific": {
            "source": "https://github.com/cleanstart-dev/cleanstart-security-advisories/blob/main/advisories/2025/CLEANSTART-2025-AY16629.json"
          }
        }
      ],
      "modified": "2026-10-08T16:47:02.827864224Z",
      "provider": "osv",
      "upstream": [
        "CVE-2018-6789"
      ],
      "references": [
        "https://github.com/cleanstart-dev/cleanstart-security-advisories/tree/main/advisories/2025/CLEANSTART-2025-AY16629.json",
        "https://osv.dev/vulnerability/CVE-2018-6789",
        "https://nvd.nist.gov/vuln/detail/CVE-2018-6789"
      ],
      "provider_metadata": {}
    },
    "related_cves": [
      {
        "value": "CVE-2018-6789",
        "evidence": "/upstream"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 101708,
  "published_at": "2026-10-01T08:02:42.987+00:00"
}