MIME::Field::ParamVal up to 5.520 RFC 2231 Continuation multipart_boundary input validation

Summaryinfo

A vulnerability, which was classified as problematic, was found in MIME::Field::ParamVal up to 5.520. This affects the function multipart_boundary of the component RFC 2231 Continuation Handler. Executing a manipulation can lead to input validation. This vulnerability is tracked as CVE-2026-116265. The attack can be launched remotely. No exploit exists. You should upgrade the affected component.

Detailsinfo

A vulnerability classified as problematic was found in MIME::Field::ParamVal up to 5.520. This vulnerability affects the function multipart_boundary of the component RFC 2231 Continuation Handler. The manipulation with an unknown input leads to a input validation vulnerability. The CWE definition for the vulnerability is CWE-20. The product receives input or data, but it does not validate or incorrectly validates that the input has the properties that are required to process the data safely and correctly. As an impact it is known to affect integrity. CVE summarizes:

MIME::Field::ParamVal versions before 5.521 for Perl do not flag an ambiguous multipart boundary written as RFC 2231 continuations. The boundary ambiguity checks look only at a plain boundary= parameter, and a boundary split into RFC 2231 sections (boundary*0=, boundary*1= and so on) is joined after they have run. A repeated section number is concatenated rather than reported as a duplicate. From version 5.518, an encoded word or trailing whitespace in such a boundary also goes unflagged, although multipart_boundary() decodes or strips it. A remote sender can make MIME::Parser split a message on a different boundary than other mail readers, hiding an attachment from a filter that relies on ambiguous_content() while the recipient's mail client shows it.

The advisory is available at metacpan.org. This vulnerability was named CVE-2026-116265 since 10/25/2026. The exploitation appears to be easy. The attack can be initiated remotely. No form of authentication is required for a successful exploitation. Technical details are known, but there is no available exploit.

Upgrading to version 5.521 eliminates this vulnerability.

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Productinfo

Name

• MIME::Field::ParamVal

Version

• 5.520

CPE 2.3info

• 🔒

CPE 2.2info

• 🔒

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