CVE-2023-35179
📋 TL;DR
This vulnerability allows attackers with administrator access to Serv-U to bypass multi-factor authentication (MFA/2FA). It affects Serv-U 15.4 installations where MFA is enabled, potentially allowing unauthorized access to administrative functions.
💻 Affected Systems
- SolarWinds Serv-U
📦 What is this software?
Serv U by Solarwinds
⚠️ Risk & Real-World Impact
Worst Case
An attacker with compromised administrator credentials could disable MFA protection entirely, gaining persistent unauthorized access to the Serv-U administrative interface and potentially compromising the entire file transfer infrastructure.
Likely Case
An insider threat or attacker with stolen admin credentials bypasses MFA to access administrative functions, potentially modifying configurations, accessing sensitive files, or creating backdoor accounts.
If Mitigated
With proper access controls and monitoring, the impact is limited to alerting on suspicious administrative activity and preventing lateral movement.
🎯 Exploit Status
Requires administrator credentials. The vulnerability is in the MFA bypass mechanism itself.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Serv-U 15.4 Hotfix 1
Vendor Advisory: https://support.solarwinds.com/SuccessCenter/s/article/Serv-U-15-4-Hotfix-1?language=en_US
Restart Required: Yes
Instructions:
1. Download Serv-U 15.4 Hotfix 1 from SolarWinds. 2. Backup current configuration. 3. Apply the hotfix following SolarWinds installation instructions. 4. Restart Serv-U services.
🔧 Temporary Workarounds
Disable MFA temporarily
allTemporarily disable multi-factor authentication until patching can be completed
Restrict administrative access
allLimit administrative access to trusted networks and implement additional authentication layers
🧯 If You Can't Patch
- Implement network segmentation to isolate Serv-U administrative interfaces
- Enhance monitoring of administrative login attempts and MFA bypass attempts
🔍 How to Verify
Check if Vulnerable:
Check Serv-U version in administrative interface. If version is 15.4 and MFA is enabled, the system is vulnerable.Check Version:
In Serv-U admin interface: Help > About Serv-UVerify Fix Applied:
Verify Serv-U version shows 15.4 Hotfix 1 or later in administrative interface.📡 Detection & Monitoring
Log Indicators:
- Unusual administrative login patterns
- MFA bypass attempts in authentication logs
- Administrative configuration changes without MFA prompts
Network Indicators:
- Administrative interface access from unexpected sources
- Multiple authentication attempts to admin endpoints
SIEM Query:
source="serv-u" AND (event_type="authentication" AND mfa_status="bypassed") OR (event_type="admin_login" AND mfa_required="true" AND mfa_used="false")🔗 References
- https://support.solarwinds.com/SuccessCenter/s/article/Serv-U-15-4-Hotfix-1?language=en_US
- https://www.solarwinds.com/trust-center/security-advisories/CVE-2023-35179
- https://support.solarwinds.com/SuccessCenter/s/article/Serv-U-15-4-Hotfix-1?language=en_US
- https://www.solarwinds.com/trust-center/security-advisories/CVE-2023-35179
