Bug 2563066 (CVE-2026-116269)

Summary: CVE-2026-116269 perl-MIME-tools: perl-MIME-tools: Attachment filter bypass via improper filename decoding
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
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Priority: medium    
Version: unspecifiedCC: rhel-process-autobot, watson-tool-maintainers
Target Milestone: ---Keywords: Security
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Hardware: All   
OS: Linux   
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A flaw was found in MIME-tools. When parsing email attachment filenames that contain hyphenated language tags, the decoder fails to properly process the character set and incorrectly returns an empty filename. A remote attacker can exploit this flaw by sending a specially crafted email message to bypass file extension security controls. As a result, restricted or malicious file attachments may pass undetected through email filtering systems and reach end users.
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Bug Depends On: 2563405    
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Description OSIDB Bzimport 2026-10-28 17:45:37 UTC 
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.