Critical Flask-CORS Vulnerabilities: Patch Update Guide (CVE-2024-6839, CVE-2024-6221, CVE-2024-6866)

 

Flask-CORS vulnerabilities (CVE-2024-6839, CVE-2024-6221, CVE-2024-6866) expose sensitive data and authentication bypass risks. Learn patching steps for Ubuntu 20.04-25.04, exploit details, and how Ubuntu Pro extends security coverage.

Overview: High-Risk Flask-CORS Security Flaws

The Flask-CORS extension, a critical middleware for handling Cross-Origin Resource Sharing (CORS) in Python web apps, was found to contain multiple high-severity vulnerabilities affecting Ubuntu LTS releases. These flaws could allow attackers to:

• Leak sensitive data via regex mishandling (CVE-2024-6839)

• Bypass authentication through path-matching errors (CVE-2024-6866)

• Exploit overly permissive default CORS headers (CVE-2024-6221)

Why should you care?

 

Flask-CORS is used in 68% of Python-based APIs (Source: PyPI 2025 Stats). Unpatched systems risk credential theft, API hijacking, and compliance violations.

---

Vulnerability Breakdown & Impact

1. CVE-2024-6839: Regex Handling Exploit

• Risk: Remote data exfiltration

• Root Cause: Improper validation of regex patterns in CORS policies.

• Affected Versions: All Ubuntu releases prior to patched updates.

2. CVE-2024-6221: Overly Permissive Default Headers

• Risk: Unauthorized cross-origin requests

• Ubuntu-Specific: Only impacts 20.04 LTS, 22.04 LTS, 24.04 LTS, and 24.10.

3. CVE-2024-6866: Path Matching Case Sensitivity

• Risk: Authentication bypass via URL path manipulation.

---

Patch Instructions for Ubuntu

Step-by-Step Update Guide

Upgrade to these patched versions immediately:

Ubuntu Release	Package Version
25.04 (Plucky)	python3-flask-cors 5.0.0-1ubuntu0.1
24.10 (Oracular)	python3-flask-cors 4.0.1-1ubuntu0.1
24.04 (Noble)	python3-flask-cors 4.0.0-1ubuntu0.1~esm1

Terminal Command:

bash

sudo apt update && sudo apt install python3-flask-cors  

---

Enhanced Protection with Ubuntu Pro

For extended security coverage (10 years) across 25,000+ Main/Universe packages:

• Free for up to 5 machines

• Includes ESM (Extended Security Maintenance) for legacy systems.

👉 Get Ubuntu Pro

---

FAQ: Flask-CORS Vulnerabilities

Q: Can these vulnerabilities lead to full system compromise?

A: While they primarily enable data leaks, combined with other flaws (e.g., XSS), attackers could escalate privileges.

Q: Are non-Ubuntu systems affected?

A: Yes, but Canonical’s advisory specifically addresses Ubuntu packages. Check Flask-CORS GitHub for upstream fixes.