AIKIDO-2026-653585
marcel is vulnerable to Interpretation Conflict
30
Low Risk
This Affects:
marcelTL;DR
Marcel's parse_media_type accepted loosely tokenized declared_type values, so malformed Content-Type strings, comma-separated lists, invalid encodings, and inputs larger than 8 KiB were treated as real media types. HTML and XHTML magic also matched unanchored markup anywhere in the sample, so container formats with later HTML-like bytes were labeled text/html while some genuine HTML was not. Applications that store and serve the sniffed type, can therefore attach the wrong Content-Type to untrusted uploads. The fix validates declared types against a single well-formed media-type grammar, bounds them to 8 KiB, and matches HTML and XHTML only from bounded opening-tag patterns.
Who does this affect?
You are affected if you are using a version that falls within the vulnerable range and your application uses Marcel to identify MIME types of untrusted uploads and relies on the returned type for serving or allowlisting.
Background info
marcel is vulnerable to Interpretation Conflict in versions 0.3.0 - 1.2.1.
How to fix this
Upgrade the marcel library to the patch version.
Are You Affected?
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SOC 2Compliant
ISO 27001CompliantISO 42001Compliant
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