jugmac00 Flask-Reuploaded up to 1.5.x Extension flask_uploads.py UploadSet.save Name incomplete blacklist

Summaryinfo

A vulnerability labeled as critical has been found in jugmac00 Flask-Reuploaded up to 1.5.x. The impacted element is the function UploadSet.save of the file src/flask_uploads/flask_uploads.py of the component Extension Handler. Executing a manipulation of the argument Name can lead to incomplete blacklist. This vulnerability is registered as CVE-2026-54567. It is possible to launch the attack remotely. No exploit is available. The affected component should be upgraded.

Detailsinfo

A vulnerability was found in jugmac00 Flask-Reuploaded up to 1.5.x. It has been declared as critical. This vulnerability affects the function UploadSet.save of the file src/flask_uploads/flask_uploads.py of the component Extension Handler. The manipulation of the argument name with an unknown input leads to a incomplete blacklist vulnerability. The CWE definition for the vulnerability is CWE-184. The product implements a protection mechanism that relies on a list of inputs (or properties of inputs) that are not allowed by policy or otherwise require other action to neutralize before additional processing takes place, but the list is incomplete, leading to resultant weaknesses. As an impact it is known to affect confidentiality, integrity, and availability. CVE summarizes:

Flask-Reuploaded provides file uploads for Flask. From 1.5.0 until 1.6.0, UploadSet.save(storage, name=...) in src/flask_uploads/flask_uploads.py applies lowercase_ext to the default upload path but uses the case-preserving extension helper for a caller-supplied name before extension_allowed evaluates an AllExcept denylist. An attacker who controls the name override can use a mixed-case dangerous extension to bypass a lowercase denylist and store the file in the served upload directory. Exploitation requires a denylist configuration, a user-influenced name override, and a deployment that resolves or executes extensions case-insensitively; pure allowlists remain protected and path containment is not bypassed. On an execution-capable upload directory, the stored file can execute with the web server's privileges and affect confidentiality, integrity, and availability. This issue is fixed in version 1.6.0.

The advisory is available at github.com. This vulnerability was named CVE-2026-54567 since 06/15/2026. The exploitation appears to be easy. The attack can be initiated remotely. Technical details are known, but there is no available exploit. This vulnerability is assigned to T1562.006 by the MITRE ATT&CK project.

Upgrading to version 1.6.0 eliminates this vulnerability.

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Productinfo

Vendor

• jugmac00

Name

• Flask-Reuploaded

Version

• 1.0
• 1.1
• 1.2
• 1.3
• 1.4
• 1.5

Website

• Product: https://github.com/jugmac00/flask-reuploaded/

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