Inadequate Password Complexity Enforcement Vulnerability
Introduction
During my journey as a security enthusiast, I recently identified a minor vulnerability related to verbose error messages that could lead to information leakage. This write-up provides a detailed breakdown of the issue, including technical steps, the impact of the vulnerability, and the solutions implemented to address it.
The Vulnerability
Verbose error messages occur when an application’s error handling mechanism reveals excessive details about the internal configuration. While this information alone might not be immediately exploitable, it can be leveraged to refine attacks, map the system, or uncover other vulnerabilities.
How It Worked
Triggering the Error:
A user submits invalid input or triggers an error condition (e.g., failed login attempt, missing resource).
Information Leakage:
Instead of displaying a generic error message, the server returns a verbose error message containing internal system details, such as:
- Full database table names
- File paths
- Library or framework versions
- Stack traces
Key Flaw
The system failed to restrict the information shared in error messages, inadvertently exposing sensitive internal details. This lack of sanitization allowed potential attackers to use the error output for reconnaissance.
Technical Details
Vulnerable Endpoint:
https://example.com/login
Exploitation Steps:
-
Submit invalid login credentials or manipulate the input in a way that triggers an error.
-
Observe the verbose error response, which may look like this:
Warning: mysqli_connect(): (HY000/1045): Access denied for user 'admin'@'localhost' (using password: YES) in /var/www/html/login.php on line 13
-
The above message reveals:
- The database type (
mysqli
) - The database username (
admin
) - The server file path (
/var/www/html/
) - The exact file and line where the error occurred (
login.php on line 13
)
- Use the information to:
- Map the server's file structure.
- Identify specific database users or configuration details.
- Determine the versions of frameworks or libraries in use, which could be vulnerable to known exploits.
Result
The verbose error messages exposed valuable internal details that could help an attacker:
- Develop targeted attacks, such as SQL injection, by knowing the database schema.
- Exploit server misconfigurations using revealed file paths.
- Leverage outdated software versions if identified in error responses.
Impact
Although verbose error messages are not critical vulnerabilities, they can facilitate more severe attacks. Potential risks include:
- Brute-forcing exposed database credentials.
- Exploiting known vulnerabilities in the identified software versions.
- Leveraging file paths for directory traversal or code injection attacks.
Resolution
After reporting the vulnerability to the application’s team, the issue was resolved by implementing the following measures:
- Server-Side Logging: Detailed error messages are logged on the server for debugging purposes but are not exposed to users.
- Generic Error Messages: Users only see non-descriptive messages like "An error occurred. Please try again later."
- Input Validation: Enhanced validation mechanisms were implemented to minimize error occurrences in the first place.
Lessons Learned
Secure Error Handling:
Error messages must be clear for users but should avoid sharing sensitive internal details.
Validate and Sanitize:
All inputs should be thoroughly validated to prevent errors and reduce opportunities for exploitation.
Proactive Testing:
Regular testing of error handling mechanisms is crucial to avoid unintentional information disclosure.
Bug Bounty Insights
Even seemingly minor vulnerabilities like verbose error messages can create a chain of attack vectors. Reporting and resolving these issues significantly strengthens the security posture of an application.
Conclusion
This experience highlighted the importance of secure error handling and demonstrated how minor oversights can lead to larger security risks. Reporting such vulnerabilities not only improves application security but also reinforces trust between users and platforms.