CVE-2021-23393

Description

This affects the package Flask-Unchained before 0.9.0. When using the the _validate_redirect_url function, it is possible to bypass URL validation and redirect a user to an arbitrary URL by providing multiple back slashes such as \\\evil.com/path. This vulnerability is only exploitable if an alternative WSGI server other than Werkzeug is used, or the default behaviour of Werkzeug is modified using 'autocorrect_location_header=False.

How to fix CVE-2021-23393

To remediate CVE-2021-23393, upgrade the affected package to a fixed version below.

• —upgrade to 0.9.0 or later
• —upgrade to 71e36b28166f9ffbe0a991f51127f0984f7e6a40 or later

Is CVE-2021-23393 being exploited?

Low — EPSS is 0.2%, meaning exploitation activity has not been observed at scale.

Affected packages (2)

• from 0, < 0.9.0
• from 0, < 71e36b28166f9ffbe0a991f51127f0984f7e6a40 | from 0, < 0.9.0

CVSS scores

References (6)

• ADVISORYgithub.com/advisories/GHSA-pjc4-3w99-j7v4
• ADVISORYnvd.nist.gov/vuln/detail/CVE-2021-23393
• WEBgithub.com/briancappello/flask-unchained/commit/2bfeedf1bc31df851cab8c66df0c432b10406aad
• WEBgithub.com/briancappello/flask-unchained/commit/71e36b28166f9ffbe0a991f51127f0984f7e6a40