CVE-2025-28104
📋 TL;DR
An incorrect access control vulnerability in flaskBlog v2.6.1 allows unauthenticated attackers to retrieve all usernames via crafted input. This affects all deployments using the vulnerable version, potentially exposing user identities and enabling further attacks. The vulnerability stems from improper authorization checks in user enumeration endpoints.
💻 Affected Systems
- flaskBlog
📦 What is this software?
Flaskblog by Dogukanurker
⚠️ Risk & Real-World Impact
Worst Case
Attackers could enumerate all user accounts, then use this information for targeted credential stuffing, social engineering, or brute-force attacks against administrative accounts, potentially leading to full system compromise.
Likely Case
Attackers will harvest usernames to build targeted attack lists, potentially compromising user accounts through password spraying or credential stuffing attacks.
If Mitigated
With proper network segmentation and strong authentication controls, impact is limited to exposure of usernames only, though this still violates privacy expectations.
🎯 Exploit Status
The GitHub issue includes technical details that could be easily weaponized. No authentication is required to exploit this vulnerability.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Not available
Vendor Advisory: Not available
Restart Required: No
Instructions:
1. Monitor the official flaskBlog repository for security updates. 2. Consider migrating to a maintained alternative if no patch is forthcoming. 3. Apply workarounds immediately.
🔧 Temporary Workarounds
Implement Web Application Firewall Rules
allBlock requests to user enumeration endpoints using WAF rules or reverse proxy configuration.
# Example nginx location block
location ~* /api/users {
deny all;
return 403;
}
# Example Apache .htaccess
RewriteRule ^api/users.*$ - [F,L]
Add Authentication Middleware
allImplement authentication checks before processing user-related API requests.
# Python Flask example decorator
from functools import wraps
from flask import request, abort
def require_auth(f):
@wraps(f)
def decorated(*args, **kwargs):
if not request.headers.get('Authorization'):
abort(401)
return f(*args, **kwargs)
return decorated
# Apply to vulnerable routes
@app.route('/api/users')
@require_auth
def get_users():
# existing code
🧯 If You Can't Patch
- Implement network segmentation to isolate the flaskBlog instance from sensitive systems.
- Deploy rate limiting and monitoring on user enumeration endpoints to detect and block exploitation attempts.
🔍 How to Verify
Check if Vulnerable:
Send a GET request to /api/users endpoint without authentication. If it returns a list of usernames, the system is vulnerable.Check Version:
Check the application's version file or package metadata. For Python: pip show flaskblog | grep VersionVerify Fix Applied:
Repeat the vulnerable request. It should return 401 Unauthorized or 403 Forbidden instead of user data.📡 Detection & Monitoring
Log Indicators:
- Multiple GET requests to /api/users endpoint from single IP
- 401/403 errors on user enumeration endpoints after fix implementation
- Unusual traffic patterns to user-related API endpoints
Network Indicators:
- HTTP requests to /api/users without authentication headers
- Burst of requests to user enumeration endpoints
SIEM Query:
source="web_logs" AND (uri_path="/api/users" OR uri_path="/api/users/*") AND http_method="GET" AND NOT http_user_agent contains "monitoring" | stats count by src_ip