{"id":"CVE-2026-116265","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.\n\nThe boundary ambiguity checks look only at a plain boundary= parameter, and a boundary split into RFC 22…","severity":"none","cwe":["CWE-436"],"product":"MIME-tools","affected":["MIME-tools < 5.521"],"published":"2026-10-28","updated":"2026-10-28","sourceUpdated":"2026-10-28T17:32:11.827Z","source":"CVEORG","sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-116265","references":[{"url":"https://metacpan.org/release/DSKOLL/MIME-tools-5.521/changes"}],"tags":["cve.org"],"ingestedAt":"2026-10-28T18:15:46.384Z","slug":"CVE-2026-116265","body":"## Overview\n\nMIME::Field::ParamVal versions before 5.521 for Perl do not flag an ambiguous multipart boundary written as RFC 2231 continuations.\n\nThe 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.\n\nA 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.\n\n## Affected\n\n- `MIME-tools < 5.521`\n\n## Remediation\n\nUpgrade to MIME-tools 5.521 or later.","depth":"sunlit","depthScore":3,"depthScoreParts":{"impact":2.8,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[]}