CVE-2023-2106
📋 TL;DR
CVE-2023-2106 is a critical authentication vulnerability in Calibre-Web that allows attackers to bypass weak password requirements and gain unauthorized access. This affects all users running Calibre-Web versions prior to 0.6.20. Attackers can exploit insufficient password strength validation to compromise user accounts.
💻 Affected Systems
- Calibre-Web
📦 What is this software?
Calibre Web by Janeczku
⚠️ Risk & Real-World Impact
Worst Case
Complete system compromise where attackers gain administrative access, steal sensitive data, modify content, and potentially pivot to other systems.
Likely Case
Unauthorized access to user accounts leading to data theft, privilege escalation, and potential manipulation of the Calibre-Web instance.
If Mitigated
Limited impact with strong network segmentation, proper access controls, and monitoring in place to detect unauthorized access attempts.
🎯 Exploit Status
Exploitation requires user registration or password reset functionality to be enabled. Attackers can brute-force or guess weak passwords due to insufficient validation.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 0.6.20
Vendor Advisory: https://github.com/janeczku/calibre-web/commit/49e4f540c9b204c7e39b3c27ceadecd83ed60e7e
Restart Required: Yes
Instructions:
1. Backup your current Calibre-Web installation and database. 2. Stop the Calibre-Web service. 3. Update to version 0.6.20 using git pull or download the release. 4. Restart the Calibre-Web service. 5. Verify the update was successful.
🔧 Temporary Workarounds
Enforce Strong Password Policy
allImplement external password policy enforcement through reverse proxy or application firewall
# Configure nginx/apache to enforce password complexity
# Use mod_security or similar WAF rules
Disable User Registration
allTemporarily disable new user registration to prevent account creation attacks
# Set ENABLE_REGISTRATION = False in config file
# Restart Calibre-Web service
🧯 If You Can't Patch
- Implement network segmentation to isolate Calibre-Web from critical systems
- Enable detailed authentication logging and monitor for suspicious login attempts
🔍 How to Verify
Check if Vulnerable:
Check Calibre-Web version in web interface or configuration file. Versions below 0.6.20 are vulnerable.Check Version:
grep -i version /path/to/calibre-web/app/__init__.py or check web interface footerVerify Fix Applied:
Verify version is 0.6.20 or higher and test password complexity requirements by attempting to set weak passwords.📡 Detection & Monitoring
Log Indicators:
- Multiple failed login attempts from single IP
- Successful logins with weak/common passwords
- User registration attempts with weak passwords
Network Indicators:
- Unusual authentication traffic patterns
- Brute-force attack signatures
SIEM Query:
source="calibre-web" (event="login_failed" OR event="user_registered") | stats count by src_ip, user🔗 References
- https://github.com/janeczku/calibre-web/commit/49e4f540c9b204c7e39b3c27ceadecd83ed60e7e
- https://huntr.dev/bounties/c3d5c647-7557-40a9-aee4-24dc14882781
- https://github.com/janeczku/calibre-web/commit/49e4f540c9b204c7e39b3c27ceadecd83ed60e7e
- https://huntr.dev/bounties/c3d5c647-7557-40a9-aee4-24dc14882781
