MIME::Field::ParamVal versions before 5.521 for Perl do not flag an ambiguous multipart boundary written as RFC 2231 continuations

{
  "id": "a729e74dec73f8bfbce8ec47c62c287837e8f3aa4fe10078e826ea6307a6d98c",
  "url": "https://www.cve.org/CVERecord?id=CVE-2026-116265",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "MIME::Field::ParamVal versions before 5.521 for Perl do not flag an ambiguous multipart boundary written as RFC 2231 continuations",
    "summary": "MIME::Field::ParamVal versions before 5.521 for Perl do not flag an ambiguous multipart boundary written as RFC 2231 continuations. The boundary ambiguity checks look only at a plain boundary= parameter, and a boundary split into RFC 2231 sections (boundary*0=, boundary*1= and so on) is joined after they have run. A repeated section number is concatenated rather than reported as a duplicate. From version 5.518, an encoded word or trailing whitespace in such a boundary also goes unflagged, although multipart_boundary() decodes or strips it. A remote sender can make MIME::Parser split a message on a different boundary than other mail readers, hiding an attachment from a filter that relies on ambiguous_content() while the recipient's mail client shows it.",
    "evidence": "cve:CVE-2026-116265",
    "products": [],
    "severity": "unknown",
    "structured": {
      "id": "CVE-2026-116265",
      "aliases": [
        "CVE-2026-116265"
      ],
      "metrics": [],
      "affected": [
        {
          "repo": "https://salsa.debian.org/dskoll/mime-tools",
          "modules": [
            "MIME::Field::ParamVal"
          ],
          "versions": [
            {
              "status": "affected",
              "version": "0",
              "lessThan": "5.521",
              "versionType": "custom"
            }
          ],
          "packageURL": "pkg:cpan/MIME-tools",
          "packageName": "MIME-tools",
          "programFiles": [
            "lib/MIME/Field/ParamVal.pm"
          ],
          "collectionURL": "https://cpan.org/modules",
          "defaultStatus": "unaffected",
          "programRoutines": [
            {
              "name": "MIME::Field::ParamVal::parse_params"
            }
          ]
        }
      ],
      "modified": "2026-10-28T17:32:11.827Z",
      "provider": "cve",
      "references": [
        "https://metacpan.org/release/DSKOLL/MIME-tools-5.521/changes"
      ],
      "provider_metadata": {
        "cna": {
          "orgId": "9b29abf9-4ab0-4765-b253-1875cd9b441e",
          "shortName": "CPANSec",
          "dateUpdated": "2026-10-28T17:32:11.827Z"
        }
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-116265",
        "evidence": "/cveMetadata/cveId"
      }
    ],
    "security_relevant": true,
    "severity_evidence": null
  },
  "source_id": "core-cve",
  "document_id": 466441,
  "published_at": "2026-10-28T17:32:11.827+00:00"
}