CVE-2020-25032: 
Python vulnerability analysis and mitigation

CVE-2020-25032 is a directory traversal vulnerability discovered in Flask-CORS (CORS Middleware for Flask) versions before 3.0.9. The vulnerability was disclosed on August 31, 2020, affecting the Flask-CORS package which handles Cross Origin Resource Sharing (CORS) in Flask applications. The issue allows attackers to use '../' directory traversal to access private resources because resource matching does not ensure that pathnames are in a canonical format (NVD, MITRE).

The vulnerability stems from Flask-CORS incorrectly evaluating CORS resource matching before path expansion. For example, a path like '/api/../foo.txt' would incorrectly match resources for '/api/*' whereas the path actually expands to '/foo.txt'. The vulnerability has been assigned a CVSS v3.1 base score of 7.5 (High), with the vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N, indicating it is network accessible, requires low attack complexity, and can be exploited without authentication (NVD).

The vulnerability allows attackers to bypass intended access restrictions and potentially expose sensitive information by accessing private resources that should be restricted. This could lead to unauthorized access to confidential data stored in the application (Debian).

The vulnerability is remotely exploitable without requiring authentication. An attacker can exploit this issue by sending specially crafted requests containing directory traversal sequences to bypass resource matching rules (NVD).

The vulnerability was fixed in Flask-CORS version 3.0.9. The fix includes properly escaping paths before evaluating resource rules. Organizations using affected versions should upgrade to version 3.0.9 or later. Various Linux distributions have also released security updates to address this vulnerability in their packages (Flask-CORS Release).