CVE-2018-7830 in M340
Summary
by MITRE
Improper Neutralization of CRLF Sequences in HTTP Headers ('HTTP Response Splitting') vulnerability exists in the embedded web servers in all Modicon M340, Premium, Quantum PLCs and BMXNOR0200 where a denial of service can occur for ~1 minute by sending a specially crafted HTTP request.
Be aware that VulDB is the high quality source for vulnerability data.
Analysis
by VulDB Data Team • 04/16/2020
The CVE-2018-7830 vulnerability represents a critical HTTP response splitting flaw affecting embedded web servers within several Modicon PLC models including M340, Premium, and Quantum series along with BMXNOR0200 units. This vulnerability stems from improper handling of CRLF (Carriage Return Line Feed) sequences within HTTP headers, creating a pathway for malicious actors to manipulate HTTP responses. The flaw specifically impacts the embedded web server implementations found in these industrial control devices, which are commonly deployed in critical infrastructure environments where reliability and security are paramount. The vulnerability allows attackers to inject malicious content into HTTP headers by exploiting the lack of proper input validation and sanitization mechanisms.
The technical exploitation of this vulnerability occurs when an attacker crafts a specially formatted HTTP request containing CRLF sequences within header values. When the embedded web server processes this malformed request, it fails to properly neutralize the CRLF characters, leading to the injection of additional HTTP headers or response content. This creates a condition where the server's response can be split into multiple distinct responses, potentially allowing for cache poisoning, session hijacking, or more specifically in this case, denial of service conditions. The vulnerability is classified under CWE-113, which specifically addresses improper neutralization of CRLF sequences in HTTP headers, making it a direct implementation of the well-known HTTP response splitting attack vector. The attack follows patterns consistent with the MITRE ATT&CK framework's technique T1190, which involves exploiting vulnerabilities in web applications to manipulate HTTP responses.
The operational impact of this vulnerability extends beyond simple service disruption, particularly in industrial control environments where these PLCs serve as critical components of operational technology infrastructure. When exploited, the vulnerability causes a denial of service condition lasting approximately one minute, during which the affected web server becomes unresponsive to legitimate requests. This disruption can have cascading effects on industrial processes that rely on web-based interfaces for monitoring and control, potentially leading to operational downtime and reduced system availability. The embedded nature of these web servers within industrial control systems means that traditional network security measures may not be sufficient to prevent exploitation, as the vulnerability exists within the device firmware itself rather than at the network perimeter. The vulnerability affects devices that are typically deployed in environments where physical security and network isolation are critical, but where the presence of web interfaces creates additional attack surfaces that may not be properly secured.
Mitigation strategies for CVE-2018-7830 should focus on both immediate remediation and long-term security enhancements. The primary recommendation involves applying manufacturer-provided firmware updates that address the specific CRLF handling issue within the embedded web server implementations. Organizations should also implement network segmentation to isolate these devices from general network traffic and consider deploying web application firewalls that can detect and block malformed HTTP requests containing CRLF sequences. Access controls should be strengthened to limit who can submit requests to the embedded web servers, and network monitoring should be enhanced to detect unusual traffic patterns that might indicate exploitation attempts. Additionally, regular security assessments of industrial control systems should include evaluation of embedded web server components, as these often represent overlooked security surfaces in OT environments. The vulnerability highlights the importance of secure coding practices in embedded systems and the need for proper input validation, particularly for components that handle network communications in industrial environments where the stakes of service disruption are extremely high.