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CVE-2026-116272                                      CPAN Security Group
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         CVE ID:  CVE-2026-116272

   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 do not flag a
duplicate boundary parameter whose name contains a nested comment

Description
-----------
MIME::Field::ParamVal versions before 5.521 for Perl do not flag a
duplicate boundary parameter whose name contains a nested comment.

A parameter written boundary((c))="A" or boundary(\))="A" is stored
under that literal name rather than as boundary. A second boundary
parameter is then not reported as a duplicate, and MIME::Parser splits
the message on it.

Readers that skip comments as RFC 5322 allows take the first boundary
instead. 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