Grandstream UCM6200 Series IP PBX Unauthenticated Remote SQL Injection and RCE Vulnerability (CVE-2020-5722) Analysis & Mitigation Guide
Executive & SecOps Summary
SECOPS ASSESSMENTGrandstream UCM6200 series IP PBX (RCE as root in versions prior to 1.0.19.20; HTML injection in versions prior to 1.0.20.17)
Unauthenticated remote attackers can execute arbitrary shell commands with root privileges or inject malicious HTML into password recovery emails via crafted HTTP requests.
Immediately upgrade the device firmware to the latest secure version (1.0.20.17 or higher) and restrict external access to the management interface.
Affected Products & Version Scope
Remediation & Live Workaround Commands
PATCH & WORKAROUND1. Official Patch & Version Upgrade Commands
Administrators must upgrade the Grandstream UCM6200 series firmware to version 1.0.20.17 or later. While upgrades are typically performed via the Web GUI, the following CLI commands illustrate configuring the official Grandstream firmware server for an update:
# Access the UCM6200 CLI via SSH and configure the update parameters
# Note: Ensure a full configuration backup is taken before proceeding.
config t
upgrade protocol http
upgrade server firmware.grandstream.com
upgrade path /
write
# Trigger the system upgrade immediately
upgrade system now2. Temporary Workaround & Hardening Configuration
If an immediate firmware upgrade is not feasible, restrict access to the web management interface (ports 80 and 443) using a firewall or a reverse proxy. Below is an example of restricting access to trusted administrative subnets using an Nginx configuration:
# Nginx reverse proxy configuration to restrict access to the UCM6200 web interface
server {
listen 443 ssl;
server_name ucm-admin.local;
location / {
# Restrict access to trusted internal admin subnet only
allow 10.0.10.0/24;
deny all;
proxy_pass http://<UCM6200_INTERNAL_IP>;
proxy_set_header Host $host;
proxy_set_header X-Real-IP $remote_addr;
}
}3. Log Audit & IoC Verification Commands
Inspect the web server access logs for suspicious requests targeting the password recovery endpoint containing SQL injection patterns. Run the following commands on your log analysis server:
# Search for suspicious SQL injection patterns targeting the sendPasswordEmail endpoint
grep -i 'sendPasswordEmail' /var/log/lighttpd/access.log | grep -E '(\'|\%27|\;|UNION|SELECT|INSERT)'
# Check system logs for unauthorized shell execution or root privilege escalation indicators
grep -i 'sh' /var/log/messages | grep -E '(root|admin)'Stop Exposing VPN Ports to the Internet — Switch to Zero-Trust Access
Eliminate public-facing VPN concentrators and firewall management ports with identity-first Zero-Trust Network Access.
Technical Root Cause & Exploitation Mechanics
1. Vulnerability Overview & Root Cause
This vulnerability (CVE-2020-5722) is a critical unauthenticated SQL injection vulnerability residing in the HTTP management interface of Grandstream UCM6200 series IP PBX devices. The root cause lies in the insufficient sanitization of user-supplied input within the password recovery functionality (specifically the sendPasswordEmail endpoint) before incorporating it into database queries. This allows remote attackers to manipulate SQL queries without any authentication.
2. Exploitation Mechanics & Attack Scenario
An attacker can exploit this vulnerability by sending a specially crafted HTTP POST request containing malicious SQL payloads to the vulnerable web interface endpoint. In firmware versions prior to 1.0.19.20, the SQL injection vulnerability can be chained to execute arbitrary operating system commands with root privileges, leading to complete system compromise. In versions prior to 1.0.20.17, the vulnerability allows attackers to inject arbitrary HTML code into password recovery emails, which can be leveraged for highly targeted credential harvesting or phishing campaigns.
3. Infrastructure & Business Impact
With a CVSS score of 9.8 (Critical) and its inclusion in the CISA Known Exploited Vulnerabilities (KEV) catalog, this vulnerability poses an active threat. Successful exploitation allows full administrative control over the IP PBX system. This can lead to severe business impacts, including unauthorized eavesdropping on corporate voice communications, theft of Call Detail Records (CDRs), toll fraud (unauthorized long-distance calls), and lateral movement into the internal corporate network using the compromised PBX as a pivot point.
Official Vendor Advisories & References
The HTTP interface of the Grandstream UCM6200 series is vulnerable to an unauthenticated remote SQL injection via crafted HTTP request. An attacker can use this vulnerability to execute shell commands as root on versions before 1.0.19.20 or inject HTML in password recovery emails in versions before 1.0.20.17.
Frequently Asked SecOps Questions (CVE-2020-5722)
FAQQ1. How critical is CVE-2020-5722 and is it actively exploited in the wild?
CVE-2020-5722 is rated CVSS 9.8 (CRITICAL) with a 30-day EPSS exploitation probability of 84.3%. It is listed in the CISA Known Exploited Vulnerabilities (KEV) catalog, requiring immediate emergency remediation.
Q2. Which vendors and products are affected by CVE-2020-5722?
Primary impacted vendors include grandstream across ucm6200, ucm6202, ucm6204, ucm6208. Scope summary: Grandstream UCM6200 Series IP PBX (including UCM6202, UCM6204, UCM6208) - Firmware versions prior to 1.0.19.20: Vulnerable to unauthenticated root-level Remote Code Execution (RCE) - Firmware versions prior to 1.0.20.17: Vulnerable to HTML injection in password recovery emails
Q3. What temporary mitigations or workarounds exist for CVE-2020-5722 before patching?
[Mitigation] Immediately upgrade the device firmware to the latest secure version (1.0.20.17 or higher) and restrict external access to the management interface. Follow the CLI remediation commands and interactive SecOps checklist on this page to restrict exposure prior to your maintenance window.
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