CVE-2024-41592: DrayTek Vigor Buffer Overflow Flaw

CVE-2024-41592 Overview

CVE-2024-41592 is a stack-based buffer overflow vulnerability affecting multiple DrayTek Vigor router models through firmware version 4.3.2.6. The vulnerability exists in the GetCGI function, which improperly handles query string parameters containing extraneous ampersand characters and excessively long key-value pairs. This flaw can be exploited by an attacker with adjacent network access to trigger memory corruption, potentially leading to arbitrary code execution or denial of service.

DrayTek routers are widely deployed in enterprise and small-to-medium business environments, making this vulnerability particularly concerning for organizations relying on these devices for network perimeter security.

Critical Impact

Successful exploitation allows attackers on the adjacent network to achieve code execution with elevated privileges on affected DrayTek routers, potentially compromising the entire network infrastructure.

Affected Products

• DrayTek Vigor3910 firmware through 4.3.2.6
• DrayTek Vigor3912 firmware through 4.3.2.6
• DrayTek Vigor2962 firmware through 4.3.2.6
• DrayTek Vigor2952 firmware through 4.3.2.6
• DrayTek Vigor2926 firmware through 4.3.2.6
• DrayTek Vigor2925 firmware through 4.3.2.6
• DrayTek Vigor2866 firmware through 4.3.2.6
• DrayTek Vigor2865 firmware through 4.3.2.6
• DrayTek Vigor2766 firmware through 4.3.2.6
• DrayTek Vigor2765 firmware through 4.3.2.6
• DrayTek Vigor2763 firmware through 4.3.2.6
• DrayTek Vigor2762 firmware through 4.3.2.6
• DrayTek Vigor2862 firmware through 4.3.2.6
• DrayTek Vigor2860 firmware through 4.3.2.6
• DrayTek Vigor2832 firmware through 4.3.2.6
• DrayTek Vigor2620 firmware through 4.3.2.6
• DrayTek Vigor2915 firmware through 4.3.2.6
• DrayTek Vigor2135 firmware through 4.3.2.6
• DrayTek Vigor2133 firmware through 4.3.2.6
• DrayTek Vigor1000B firmware through 4.3.2.6
• DrayTek Vigor166 firmware through 4.3.2.6
• DrayTek Vigor165 firmware through 4.3.2.6
• DrayTek VigorLTE200 firmware through 4.3.2.6
• DrayTek Vigor3220 firmware through 4.3.2.6

Discovery Timeline

• 2024-10-03 - CVE-2024-41592 published to NVD
• 2025-06-03 - Last updated in NVD database

Technical Details for CVE-2024-41592

Vulnerability Analysis

This vulnerability is classified as CWE-121: Stack-based Buffer Overflow. The flaw resides in the CGI processing functionality of affected DrayTek Vigor routers, specifically within the GetCGI function responsible for parsing HTTP query string parameters.

When processing incoming HTTP requests, the GetCGI function fails to properly validate the length and format of query string parameters before copying them to stack-allocated buffers. The function does not adequately handle edge cases involving multiple consecutive ampersand (&) characters or unusually long key-value pairs in the query string.

This allows an attacker to craft malicious HTTP requests that overflow stack buffers, potentially overwriting critical stack data including return addresses and saved registers.

Root Cause

The root cause lies in insufficient bounds checking within the GetCGI function. When parsing query string parameters delimited by ampersand characters, the function uses fixed-size stack buffers without properly validating that incoming data fits within allocated boundaries. The mishandling of extraneous ampersand characters exacerbates this issue by potentially causing the parser to process unintended data segments, leading to additional memory corruption scenarios.

Attack Vector

Exploitation requires adjacent network access to the affected router's web management interface. An attacker positioned on the same network segment can send crafted HTTP requests containing malicious query strings to trigger the overflow. The attack does not require authentication when the management interface is accessible.

The attacker constructs HTTP GET or POST requests with query strings containing:

• Multiple consecutive ampersand characters to confuse the parser
• Excessively long key-value pairs exceeding expected buffer sizes

When processed by the vulnerable GetCGI function, these malformed inputs overflow stack buffers, enabling the attacker to corrupt stack memory and potentially hijack program execution flow. For detailed technical analysis, refer to the Forescout Draybreak Research.

Detection Methods for CVE-2024-41592

Indicators of Compromise

• Unusual HTTP requests to router management interfaces containing excessively long query strings
• HTTP requests with abnormal patterns of ampersand characters in query parameters
• Router crashes or unexpected reboots following web management access
• Unexpected processes or network connections originating from router devices

Detection Strategies

• Deploy network intrusion detection signatures to identify HTTP requests with abnormally long query string parameters targeting DrayTek devices
• Monitor for HTTP requests containing sequences of multiple consecutive ampersand characters in query strings
• Implement web application firewall rules to block requests exceeding reasonable query string length thresholds
• Use asset inventory tools to identify all DrayTek Vigor devices and their firmware versions across the network

Monitoring Recommendations

• Enable logging on DrayTek router management interfaces and forward logs to a centralized SIEM
• Monitor for authentication failures and unusual access patterns on router management ports
• Set up alerts for router reboots or service restarts that may indicate exploitation attempts
• Review network traffic patterns for anomalous HTTP requests destined for router management interfaces

How to Mitigate CVE-2024-41592

Immediate Actions Required

• Identify all DrayTek Vigor devices in your environment using the affected product list
• Restrict access to router management interfaces to trusted administrative networks only
• Disable remote management access from untrusted network segments
• Apply firmware updates from DrayTek as they become available
• Implement network segmentation to limit adjacent network access to router management interfaces

Patch Information

DrayTek has acknowledged this vulnerability as part of the Forescout Draybreak research disclosure. Administrators should monitor DrayTek's official security advisories and download portal for firmware updates addressing CVE-2024-41592. Check the Forescout DrayTek Vulnerabilities page for additional details on affected versions and remediation guidance.

Workarounds

• Disable the web management interface entirely if not required for operations
• Configure access control lists (ACLs) to restrict management interface access to specific trusted IP addresses
• Place router management interfaces on isolated VLAN segments not accessible from general user networks
• Use VPN connections for remote administration rather than exposing management interfaces directly

# Example ACL configuration to restrict management access
# Access router via console or trusted connection
# Navigate to System Maintenance > Management
# Set "Allow Management from Internet" to disabled
# Configure LAN Management to allow only specific IP ranges
# Example: Allow only 192.168.1.100-192.168.1.105 for admin access