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CVE-2026-116264                                      CPAN Security Group
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         CVE ID:  CVE-2026-116264

   Distribution:  MIME-tools
       Versions:  before 5.521
       MetaCPAN:  https://metacpan.org/dist/MIME-tools
       VCS Repo:  https://salsa.debian.org/dskoll/mime-tools

MIME::Field::ParamVal versions before 5.521 for Perl allow one invalid
Content-Type parameter to hide the parameters after it, including the
multipart boundary

Description
-----------
MIME::Field::ParamVal versions before 5.521 for Perl allow one invalid
Content-Type parameter to hide the parameters after it, including the
multipart boundary.

Parameter parsing stops at the first parameter whose name it cannot
read, such as x:y=1 or a name containing an 8-bit byte, and drops every
parameter after it. When the boundary is among them, MIME::Parser keeps
the multipart body as a single undecoded part without marking the parse
as ambiguous.

Mail readers that skip the invalid parameter still find the boundary. A
remote sender can hide an attachment from a filter that relies on
ambiguous_content() while the recipient's mail client shows it.

Problem types
-------------
- CWE-436 Interpretation Conflict

Solutions
---------
Upgrade to MIME-tools 5.521 or later.

References
----------
https://metacpan.org/release/DSKOLL/MIME-tools-5.521/changes