CVE-2018-5440 in CODESYS Web Server
Summary
by MITRE
A Stack-based Buffer Overflow issue was discovered in 3S-Smart CODESYS Web Server. Specifically: all Microsoft Windows (also WinCE) based CODESYS web servers running stand-alone Version 2.3, or as part of the CODESYS runtime system running prior to Version V1.1.9.19. A crafted request may cause a buffer overflow and could therefore execute arbitrary code on the web server or lead to a denial-of-service condition due to a crash in the web server.
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Analysis
by VulDB Data Team • 01/06/2020
The vulnerability identified as CVE-2018-5440 represents a critical stack-based buffer overflow flaw within the 3S-Smart CODESYS Web Server implementation. This vulnerability specifically affects Microsoft Windows-based systems including Windows CE environments running standalone versions 2.3 or integrated CODESYS runtime systems prior to version 1.1.9.19. The flaw stems from inadequate input validation mechanisms within the web server's request processing pipeline, creating a condition where maliciously crafted HTTP requests can overflow stack buffers and potentially execute arbitrary code on the affected system. The vulnerability's exploitation potential extends beyond simple code execution to include denial-of-service scenarios through server crashes, making it particularly dangerous in industrial control environments where system availability is paramount.
The technical implementation of this vulnerability demonstrates a classic stack buffer overflow condition that occurs when user-supplied input exceeds the allocated buffer space during request handling. The flaw manifests in the web server's parsing of HTTP requests, where insufficient bounds checking allows attackers to overwrite adjacent stack memory locations. This type of vulnerability maps directly to CWE-121 Stack-based Buffer Overflow, which is categorized under the broader weakness type CWE-119 as a memory safety error. The attack vector requires minimal privileges since it operates at the network level, targeting the web server's HTTP interface and exploiting the lack of proper input sanitization mechanisms. The vulnerability's impact is amplified by the fact that CODESYS is commonly deployed in industrial automation and control systems where the web server component serves as a critical interface for remote configuration and monitoring.
The operational implications of CVE-2018-5440 extend significantly beyond traditional information technology environments into industrial control systems and operational technology networks. Organizations utilizing CODESYS web servers face potential unauthorized access to critical industrial processes, system compromise leading to production disruptions, and possible safety hazards in environments where industrial control systems directly impact physical processes. The vulnerability's exploitation can result in complete system compromise, allowing attackers to execute malicious code with the privileges of the web server process, which often runs with elevated permissions. This makes the vulnerability particularly attractive to attackers targeting industrial control systems, as it aligns with tactics described in the MITRE ATT&CK framework under the T1059.007 technique for command and scripting interpreter. The potential for denial-of-service attacks creates additional operational concerns, as industrial systems often cannot tolerate extended downtime, making this vulnerability particularly dangerous in environments where continuous operation is required.
Mitigation strategies for CVE-2018-5440 should prioritize immediate remediation through official vendor patches and updates to CODESYS runtime systems. Organizations must implement network segmentation to limit access to CODESYS web server interfaces, applying firewall rules to restrict HTTP traffic to authorized administrative networks only. The implementation of intrusion detection systems capable of identifying malicious request patterns targeting the web server component provides additional defense layers. Regular security assessments and vulnerability scanning should specifically target CODESYS installations to identify unpatched systems. Network monitoring solutions should be configured to detect unusual traffic patterns that may indicate exploitation attempts. Organizations should also consider implementing application whitelisting policies to restrict execution of unauthorized code on systems running CODESYS web servers. The vulnerability's nature as a buffer overflow makes it particularly susceptible to exploit prevention techniques such as stack canaries, address space layout randomization, and data execution prevention mechanisms that should be enabled on all affected systems. Security teams must also establish incident response procedures specifically addressing potential exploitation of this vulnerability in industrial control environments.