CVE-2020-15504: Sophos XG Firewall SQLI Vulnerability

CVE-2020-15504 Overview

CVE-2020-15504 is a critical SQL injection vulnerability affecting the user and admin web interfaces of Sophos XG Firewall. This vulnerability exists in firmware versions v18.0 MR1 and older, potentially allowing unauthenticated remote attackers to execute arbitrary code on affected firewall devices. The severity of this vulnerability stems from its ability to chain SQL injection with remote code execution capabilities, making it particularly dangerous for organizations relying on Sophos XG Firewall for perimeter security.

Critical Impact

This SQL injection vulnerability enables unauthenticated attackers to achieve remote code execution on Sophos XG Firewall devices through the web management interfaces, potentially compromising the entire network perimeter security infrastructure.

Affected Products

• Sophos XG Firewall Firmware v18.0 (including Maintenance Release 1)
• Sophos XG Firewall Firmware v17.5 (Maintenance Releases 1-12)
• Sophos XG Firewall Firmware versions >= 17.0

Discovery Timeline

• 2020-07-10 - CVE-2020-15504 published to NVD
• 2024-11-21 - Last updated in NVD database

Technical Details for CVE-2020-15504

Vulnerability Analysis

This vulnerability is classified as CWE-89 (SQL Injection), affecting the web-based management interfaces of Sophos XG Firewall devices. The flaw exists in both the user portal and administrator web interfaces, where user-supplied input is not properly sanitized before being incorporated into SQL queries. This lack of input validation creates an opportunity for attackers to inject malicious SQL statements that can be leveraged to execute arbitrary code on the underlying system.

The attack can be conducted remotely over the network without requiring any authentication or user interaction, making it particularly dangerous for internet-facing firewall management interfaces. Once exploited, an attacker could potentially gain complete control over the firewall device, allowing them to intercept network traffic, modify firewall rules, pivot to internal networks, or establish persistent access.

Root Cause

The root cause of CVE-2020-15504 is improper input validation and sanitization in the web interface components of Sophos XG Firewall. User-supplied data passed to the user and admin web interfaces is directly incorporated into SQL queries without proper parameterization or escaping, creating an SQL injection vector. This fundamental input validation failure allows attackers to break out of the intended query context and inject arbitrary SQL commands.

Attack Vector

The vulnerability is exploitable via network access to the Sophos XG Firewall web management interfaces. An attacker can craft malicious HTTP requests containing SQL injection payloads targeting the vulnerable input fields in either the user portal or administrator interface. The attack requires no prior authentication and no user interaction, making it suitable for automated exploitation.

The exploitation chain typically involves:

1. Identifying an internet-exposed Sophos XG Firewall web interface
2. Crafting SQL injection payloads to escape the query context
3. Leveraging database-specific functionality to achieve code execution on the underlying operating system
4. Establishing persistent access or performing malicious actions on the compromised device

Detailed technical exploitation information can be found in the Sophos Security Advisory.

Detection Methods for CVE-2020-15504

Indicators of Compromise

• Unusual or malformed HTTP requests to the XG Firewall web management interfaces containing SQL syntax characters
• Unexpected database queries or errors in firewall logs
• Unauthorized configuration changes to firewall rules or settings
• New or suspicious user accounts created on the firewall device
• Unexpected outbound network connections from the firewall device

Detection Strategies

• Monitor web server logs for requests containing common SQL injection patterns such as single quotes, UNION statements, or SQL comments
• Implement Web Application Firewall (WAF) rules to detect and block SQL injection attempts targeting the management interfaces
• Review firewall authentication logs for suspicious login attempts or unauthorized access
• Deploy network-based intrusion detection signatures for known Sophos XG exploitation patterns

Monitoring Recommendations

• Enable comprehensive logging on all Sophos XG Firewall management interfaces
• Centralize log collection to a SIEM platform for correlation and anomaly detection
• Configure alerts for failed authentication attempts and configuration changes
• Regularly audit firewall configurations for unauthorized modifications

How to Mitigate CVE-2020-15504

Immediate Actions Required

• Update Sophos XG Firewall to patched versions immediately: v18 MR-1-Build396 or v17.5 MR13
• Restrict access to the firewall management interfaces to trusted networks only
• Review firewall configurations and logs for signs of compromise
• Implement network segmentation to limit exposure of management interfaces
• Enable multi-factor authentication for administrator access where supported

Patch Information

Sophos has released security patches addressing this vulnerability. The fix is incorporated into the re-release of XG Firewall v18 MR-1 (Build396) and the v17.5 MR13 release. For all other firmware versions >= 17.0, Sophos has distributed hotfixes through their automatic update mechanism. Organizations should verify their devices have received the appropriate updates by checking the firmware version in the management console.

For detailed patch information and update instructions, refer to the Sophos Security Advisory for CVE-2020-15504.

Workarounds

• Disable external access to the XG Firewall management interfaces if not required
• Implement IP-based access control lists to restrict management interface access to authorized administrator workstations
• Deploy a jump server or VPN requirement for remote administration
• Consider implementing additional network-layer protections such as a separate management VLAN

# Recommended: Verify firmware version and ensure patches are applied
# Access the Sophos XG Firewall console and navigate to:
# System > Firmware - Verify running version is v18 MR-1-Build396 or later
# or v17.5 MR13 or later

# Restrict management interface access (example ACL concept)
# Configure Device Access settings to limit management access
# to trusted IP ranges only in the XG Firewall admin console