MIME::Field::ParamVal versions before 5.521 for Perl turn an RFC 2231 filename with a hyphenated language tag into an empty recommended filename.

A parameter such as filename*=utf-8'en-US'payload.exe is converted to an encoded word with the language tag appended to the charset. The decoder strips the language suffix only when it is a single word, so it cannot resolve the charset UTF-8*EN-US and returns an empty string. The recommended_filename() method returns that empty string rather than falling back to the name parameter.

Other mail readers return payload.exe. A remote sender can get an attachment past a policy that checks file extensions on the recommended filename.

MIME::Field::ParamVal versions before 5.521 for Perl turn an RFC 2231 filename with a hyphenated language tag into an empty recommended filename.

A parameter such as filename*=utf-8'en-US'payload.exe is converted to an encoded word with the language tag appended to the charset. The decoder strips the language suffix only when it is a single word, so it cannot resolve the charset UTF-8*EN-US and returns an empty string. The recommended_filename() method returns that empty string rather than falling back to the name parameter.

Other mail readers return payload.exe. A remote sender can get an attachment past a policy that checks file extensions on the recommended filename.

Affected: Ubuntu:14.04:LTS: libmime-tools-perl, Ubuntu:16.04:LTS: libmime-tools-perl, Ubuntu:18.04:LTS: libmime-tools-perl, Ubuntu:20.04:LTS: libmime-tools-perl, Ubuntu:22.04:LTS: libmime-tools-perl, Ubuntu:24.04:LTS: libmime-tools-perl, Ubuntu:26.10: libmime-tools-perl, Ubuntu:26.04:LTS: libmime-tools-perl

[Unknown description]