CVE-2015-0842
📋 TL;DR
CVE-2015-0842 is a SQL injection vulnerability in yubiserver versions before 0.6 that allows attackers to manipulate database queries. This can lead to authentication bypass, potentially granting unauthorized access to YubiKey authentication systems. Organizations using yubiserver for two-factor authentication are affected.
💻 Affected Systems
- yubiserver
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Complete compromise of the authentication system allowing attackers to bypass YubiKey two-factor authentication entirely, potentially gaining administrative access to protected systems.
Likely Case
Authentication bypass allowing unauthorized access to systems protected by YubiKey authentication, potentially leading to data exposure or privilege escalation.
If Mitigated
Limited impact with proper input validation and database permissions in place, though SQL injection attempts may still be logged.
🎯 Exploit Status
SQL injection vulnerabilities are well-understood and often have public exploit code available. The high CVSS score suggests exploitation is straightforward.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 0.6 and later
Vendor Advisory: http://www.include.gr/debian/yubiserver/#changelog
Restart Required: Yes
Instructions:
1. Backup current configuration and database. 2. Update yubiserver to version 0.6 or later using your package manager. 3. Restart the yubiserver service. 4. Verify the update was successful.
🔧 Temporary Workarounds
Input Validation Filter
linuxImplement strict input validation for all user-supplied parameters in the yubiserver web interface
# Requires code modification to implement parameterized queries or input sanitization
Database Permission Restriction
linuxLimit database user permissions to only necessary operations
GRANT SELECT, INSERT ON yubiserver.* TO 'yubiuser'@'localhost';
REVOKE DROP, CREATE, ALTER ON yubiserver.* FROM 'yubiuser'@'localhost';
🧯 If You Can't Patch
- Implement a web application firewall (WAF) with SQL injection protection rules
- Isolate yubiserver behind a reverse proxy with request filtering and rate limiting
🔍 How to Verify
Check if Vulnerable:
Check yubiserver version: dpkg -l | grep yubiserver or check the installed package versionCheck Version:
dpkg -l | grep yubiserver | awk '{print $3}' or check the yubiserver configuration/interfaceVerify Fix Applied:
Verify version is 0.6 or later and test authentication functionality📡 Detection & Monitoring
Log Indicators:
- Unusual SQL query patterns in database logs
- Failed authentication attempts with malformed OTP values
- Multiple authentication attempts from single source
Network Indicators:
- SQL injection patterns in HTTP requests to yubiserver endpoint
- Unusual authentication request patterns
SIEM Query:
source="yubiserver" AND (message="*SQL*" OR message="*injection*" OR status="500")