Source: cve@mitre.org
Red Lion HMI panels allow remote attackers to cause a denial of service (software exception) via an HTTP POST request to a long URI that does not exist, as demonstrated by version HMI 2.41 PLC 2.42.
Red Lion HMI panels are vulnerable to a denial-of-service (DoS) attack. An attacker can crash the device by sending a specially crafted HTTP POST request with an excessively long URI. This vulnerability can disrupt critical industrial processes, leading to operational downtime and potential financial losses.
Step 1: Target Identification: Identify a Red Lion HMI panel accessible over the network, running a vulnerable firmware version (HMI 2.41 PLC 2.42 or potentially later).
Step 2: Crafting the Malicious Request: Construct an HTTP POST request. The request should target a non-existent URI on the HMI panel. The URI should be extremely long, exceeding the expected buffer size or input validation limits.
Step 3: Payload Delivery: Send the crafted HTTP POST request to the targeted HMI panel.
Step 4: Exploitation: The HMI panel's HTTP server receives the malicious request. Due to the long URI, the server attempts to process the request, triggering the vulnerability.
Step 5: Denial of Service: The HMI panel crashes due to a software exception, rendering it unresponsive and causing a denial of service.
The vulnerability stems from inadequate input validation and error handling within the Red Lion HMI's HTTP server. Specifically, the server fails to properly handle excessively long URI strings in POST requests. When a request with a URI exceeding the internal buffer size is received, the server attempts to process it, leading to a software exception. This likely results in a buffer overflow or a similar memory corruption issue, causing the HMI panel to crash and become unresponsive. The root cause is a lack of bounds checking on the URI length before processing it. The server's logic likely attempts to allocate memory or perform operations based on the URI length without verifying that the length is within acceptable limits. This can lead to memory corruption, stack overflow, or other memory-related errors, resulting in the DoS condition.
While no specific APT groups are directly linked to this vulnerability, the ease of exploitation and the potential impact on industrial control systems (ICS) make it attractive to various threat actors. This vulnerability could be leveraged by attackers seeking to disrupt operations or cause financial damage. Not listed on CISA KEV.
Network Intrusion Detection Systems (NIDS) can be configured to detect unusually long URI strings in HTTP POST requests. Look for requests with URIs exceeding a predefined length threshold (e.g., 2048 characters).
Web Application Firewalls (WAFs) can be deployed to filter and block malicious HTTP requests with excessively long URIs.
Monitor HMI panel logs for unexpected errors, crashes, or restarts. These events could indicate a successful exploitation attempt.
Analyze network traffic for suspicious HTTP POST requests targeting non-existent URIs on the HMI panel.
Upgrade to the latest firmware version provided by Red Lion, which likely includes a fix for this vulnerability. Check Red Lion's website for available updates.
Implement input validation on the HMI panel's HTTP server to limit the length of URIs. This should prevent excessively long URIs from being processed.
Deploy a Web Application Firewall (WAF) in front of the HMI panel to filter and block malicious HTTP requests.
Segment the network to isolate the HMI panel from untrusted networks. This limits the attack surface and reduces the risk of exploitation.
Implement strong authentication and authorization mechanisms to restrict access to the HMI panel's web interface.
Regularly monitor the HMI panel's logs for suspicious activity and security events.