Vulnerability Description
MIME::Head versions from 5.518 before 5.521 for Perl decode a partly encoded multipart boundary without flagging the parse as ambiguous. The multipart_boundary() method decodes RFC 2047 encoded words anywhere in the boundary, but the ambiguity check only fires when the whole value is one encoded word. A boundary such as abc=?us-ascii?Q?def?= is used as abcdef, and ambiguous_content() returns false. Encoded words are not allowed in parameters, so other mail readers split the message on the literal value. A remote sender can hide an attachment from a filter that relies on ambiguous_content() while the recipient's mail client shows it.
Related Weaknesses (CWE)
References
FAQ
What is CVE-2026-116266?
CVE-2026-116266 is a documented vulnerability. MIME::Head versions from 5.518 before 5.521 for Perl decode a partly encoded multipart boundary without flagging the parse as ambiguous. The multipart_boundary() method decodes RFC 2047 encoded words...
How severe is CVE-2026-116266?
CVSS scoring is not yet available for CVE-2026-116266. Check NVD for updates.
Is there a patch for CVE-2026-116266?
Check the references section above for vendor advisories and patch information. Review vendor security bulletins for remediation guidance.