CVE-2019-15957
📋 TL;DR
This vulnerability allows authenticated administrators on certain Cisco Small Business RV Series Routers to execute arbitrary commands with root privileges via the web management interface. It affects users with administrative access to these routers, potentially leading to full system compromise. The issue stems from insufficient input validation in a specific field.
💻 Affected Systems
- Cisco Small Business RV Series Routers
📦 What is this software?
Rv042g Dual Gigabit Wan Vpn Firmware by Cisco
View all CVEs affecting Rv042g Dual Gigabit Wan Vpn Firmware →
⚠️ Risk & Real-World Impact
Worst Case
An attacker with administrative credentials gains full root access to the router, enabling them to steal data, modify configurations, deploy malware, or use the device as a pivot point into the network.
Likely Case
An insider threat or compromised admin account leads to command execution, allowing network disruption, credential theft, or lateral movement within the network.
If Mitigated
With strong access controls and network segmentation, impact is limited to the router itself, preventing broader network compromise.
🎯 Exploit Status
Exploitation requires administrative privileges but is straightforward once credentials are obtained; public proof-of-concept code exists.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Check Cisco advisory for specific fixed firmware versions (e.g., RV340, RV345, etc.).
Vendor Advisory: https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20191106-sbr-cominj
Restart Required: Yes
Instructions:
1. Log into the router's web interface as admin. 2. Navigate to the firmware update section. 3. Download the latest firmware from Cisco's support site. 4. Upload and apply the firmware update. 5. Reboot the router as prompted.
🔧 Temporary Workarounds
Restrict Access to Management Interface
allLimit access to the web-based management interface to trusted IP addresses only.
Configure firewall rules on the router to allow management access from specific IPs (e.g., via ACLs).
Disable Remote Management
allTurn off remote access to the web management interface if not needed.
In the router settings, disable 'Remote Management' or similar options.
🧯 If You Can't Patch
- Enforce strong, unique passwords for administrative accounts and enable multi-factor authentication if supported.
- Segment the network to isolate the router from critical systems, reducing lateral movement risk.
🔍 How to Verify
Check if Vulnerable:
Check the router's firmware version via the web interface and compare with Cisco's advisory for affected versions.Check Version:
Log into the web interface and navigate to 'Status' or 'About' to view firmware version; no direct CLI command provided in public sources.Verify Fix Applied:
After updating, verify the firmware version matches or exceeds the patched version listed in the advisory.📡 Detection & Monitoring
Log Indicators:
- Unusual command execution logs in router system logs, unexpected admin login attempts, or changes to configuration files.
Network Indicators:
- Suspicious outbound connections from the router to unknown IPs, unusual traffic patterns from the management interface.
SIEM Query:
Example: 'source="router_logs" AND (event="command_injection" OR user="admin" AND action="execute")'