Bug 2563061 (CVE-2026-116264)

Summary: CVE-2026-116264 perl-MIME-tools: perl-MIME-tools: Security filter bypass via invalid Content-Type parameter
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
Severity: medium Docs Contact:
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 perl-MIME-tools. This vulnerability allows a remote attacker to bypass email security filters by sending an email with a malformed Content-Type parameter. Because the parser halts processing upon encountering an invalid parameter name, it discards subsequent parameters, including the multipart boundary, without flagging the content as ambiguous. Consequently, security scanners fail to inspect concealed attachments that downstream email clients still render to the recipient.
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oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
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Bug Depends On: 2563412    
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Description OSIDB Bzimport 2026-10-28 17:44:43 UTC 
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.