CVE-2026-54567 (GCVE-0-2026-54567)

Vulnerability from cvelistv5 – Published: 2026-09-14 17:15 – Updated: 2026-09-16 15:22
VLAI
Title
Flask-Reuploaded: Extension-denylist bypass via case-folding asymmetry in name-override path (incomplete-fix variant of CVE-2026-27641)
Summary
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.
Severity
7.5 (High)
CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
SSVC
Exploitation: poc Automatable: no Technical Impact: total
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-09-16 15:22 UTC
CWE
  • CWE-178 - Improper Handling of Case Sensitivity
  • CWE-434 - Unrestricted Upload of File with Dangerous Type
Assigner
GitHub_M CNA under the mitre root
CNA scorecard C 72/100 over 7951 records in the last 180 days details
References
Impacted products
Vendor Product Version CPE status
jugmac00 flask-reuploaded Affected: < 1.6.0
guessed Create a notification for this product.
Show details on NVD website
To clipboard 

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