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MIME::Words versions before 5.521 for Perl allow memory exhaustion via repeated "=?" sequences in decode_mimewords

Type: advisorySources: Official CVE List

MIME::Words versions before 5.521 for Perl allow memory exhaustion via repeated "=?" sequences in decode_mimewords. For each "=?" that does not start a complete encoded word, decode_mimewords appends an error message containing the whole input string to $@. A boundary of 8,000 "=?" pairs (16,000 bytes) adds 8,000 copies of itself to $@, about 128 MB. From version 5.518, MIME::Parser decodes every multipart boundary this way, so a remote sender can exhaust the memory of the parsing process with one Content-Type header.

Products: Not specified
Affected versions: Not specified
Fixed versions: Not specified
CVEs: CVE-2026-116270
Confirmed fixed CVEs: Not specified
Updated in this feed: 1 Nov 2026, 20:24 UTC · Revision 1

Source evidence

MIME::Words versions before 5.521 for Perl allow memory exhaustion via repeated "=?" sequences in decode_mimewords

core-cve · Original source

Published 28 Oct 2026, 17:33 UTC

cve:CVE-2026-116270

Complete source record

{
  "id": "ab6c05c1763b43ed07355180fd298d50974abdef89d5cda4bf86900928b0b17e",
  "url": "https://www.cve.org/CVERecord?id=CVE-2026-116270",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "MIME::Words versions before 5.521 for Perl allow memory exhaustion via repeated \"=?\" sequences in decode_mimewords",
    "summary": "MIME::Words versions before 5.521 for Perl allow memory exhaustion via repeated \"=?\" sequences in decode_mimewords. For each \"=?\" that does not start a complete encoded word, decode_mimewords appends an error message containing the whole input string to $@. A boundary of 8,000 \"=?\" pairs (16,000 bytes) adds 8,000 copies of itself to $@, about 128 MB. From version 5.518, MIME::Parser decodes every multipart boundary this way, so a remote sender can exhaust the memory of the parsing process with one Content-Type header.",
    "evidence": "cve:CVE-2026-116270",
    "products": [],
    "severity": "unknown",
    "structured": {
      "id": "CVE-2026-116270",
      "aliases": [
        "CVE-2026-116270"
      ],
      "metrics": [],
      "affected": [
        {
          "repo": "https://salsa.debian.org/dskoll/mime-tools",
          "modules": [
            "MIME::Words"
          ],
          "versions": [
            {
              "status": "affected",
              "version": "0",
              "lessThan": "5.521",
              "versionType": "custom"
            }
          ],
          "packageURL": "pkg:cpan/MIME-tools",
          "packageName": "MIME-tools",
          "programFiles": [
            "lib/MIME/Words.pm",
            "lib/MIME/Head.pm"
          ],
          "collectionURL": "https://cpan.org/modules",
          "defaultStatus": "unaffected",
          "programRoutines": [
            {
              "name": "MIME::Words::decode_mimewords"
            },
            {
              "name": "MIME::Head::multipart_boundary"
            }
          ]
        }
      ],
      "modified": "2026-10-28T17:33:48.187Z",
      "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": "2026-10-28T17:33:48.187Z"
        }
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-116270",
        "evidence": "/cveMetadata/cveId"
      }
    ],
    "security_relevant": true,
    "severity_evidence": null
  },
  "source_id": "core-cve",
  "document_id": 466446,
  "published_at": "2026-10-28T17:33:48.187+00:00"
}