The multipart_boundary() method decodes RFC 2047 encoded words anywhere in the boundary, but the ambiguity check only fires when the whole value is one encoded word. A boundary such as abc=?us-ascii?Q?def?= is used as abcdef, and ambiguous_content() returns false.
Encoded words are not allowed in parameters, so other mail readers split the message on the literal value. A remote sender can hide an attachment from a filter that relies on ambiguous_content() while the recipient's mail client shows it.
Analysis
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Default status is the baseline for the product, each version can override it (e.g. patched versions marked unaffected).
| Vendor | Product | Default status | Versions | ||||||
|---|---|---|---|---|---|---|---|---|---|
| unaffected |
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Vendor Solution
Upgrade to MIME-tools 5.521 or later.
Tracking
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| Link | Providers |
|---|---|
| https://metacpan.org/release/DSKOLL/MIME-tools-5.521/changes |
|
Wed, 28 Oct 2026 17:45:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| Description | MIME::Head versions from 5.518 before 5.521 for Perl decode a partly encoded multipart boundary without flagging the parse as ambiguous. The multipart_boundary() method decodes RFC 2047 encoded words anywhere in the boundary, but the ambiguity check only fires when the whole value is one encoded word. A boundary such as abc=?us-ascii?Q?def?= is used as abcdef, and ambiguous_content() returns false. Encoded words are not allowed in parameters, so other mail readers split the message on the literal value. A remote sender can hide an attachment from a filter that relies on ambiguous_content() while the recipient's mail client shows it. | |
| Title | MIME::Head versions from 5.518 before 5.521 for Perl decode a partly encoded multipart boundary without flagging the parse as ambiguous | |
| Weaknesses | CWE-436 | |
| References |
|
Subscriptions
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MITRE
Status: PUBLISHED
Assigner: CPANSec
Published:
Updated: 2026-10-28T17:32:28.565Z
Reserved: 2026-10-25T18:05:02.235Z
Link: CVE-2026-116266
Vulnrichment
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NVD
Status : Received
Published: 2026-10-28T18:17:13.017
Modified: 2026-10-28T18:17:13.017
Link: CVE-2026-116266
Redhat
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OpenCVE Enrichment
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