CVE-2015-7937 in Modicon M340
Summary
by MITRE
Stack-based buffer overflow in the GoAhead Web Server on Schneider Electric Modicon M340 PLC BMXNOx and BMXPx devices allows remote attackers to execute arbitrary code via a long password in HTTP Basic Authentication data.
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Analysis
by VulDB Data Team • 05/19/2018
The CVE-2015-7937 vulnerability represents a critical stack-based buffer overflow flaw within the GoAhead web server component of Schneider Electric Modicon M340 PLC devices including BMXNOx and BMXPx series. This vulnerability specifically affects the authentication mechanism of these industrial control devices, creating a significant security risk for operational technology environments. The flaw manifests when the web server processes HTTP Basic Authentication requests containing excessively long password strings, leading to memory corruption that can be exploited by remote attackers.
The technical implementation of this vulnerability stems from inadequate input validation within the GoAhead web server's authentication handler. When a malicious actor submits an HTTP request with an overly long password parameter, the server fails to properly bounds-check the input data before copying it into a fixed-size stack buffer. This classic buffer overflow condition occurs because the implementation does not enforce maximum length limits for authentication credentials, allowing attackers to overwrite adjacent memory locations on the stack. The vulnerability is particularly concerning as it operates at the application layer of the web server stack, making it accessible through standard network protocols without requiring physical access to the device.
The operational impact of CVE-2015-7937 extends beyond simple remote code execution, fundamentally compromising the integrity and availability of industrial control systems. Attackers exploiting this vulnerability can gain full administrative control over affected PLC devices, potentially enabling them to modify critical control logic, disrupt industrial processes, or establish persistent backdoors within operational technology networks. This threat is amplified in industrial environments where these devices often operate in isolated networks but may still be accessible through legacy connections or VPNs, creating multiple potential attack vectors. The vulnerability affects Schneider Electric's Modicon M340 series, which are widely deployed in manufacturing, energy, and process control applications where system reliability and security are paramount.
Mitigation strategies for CVE-2015-7937 should prioritize immediate firmware updates from Schneider Electric, as the vendor has released patches addressing this specific vulnerability. Network segmentation and access controls should be implemented to limit exposure of these devices to untrusted networks, while monitoring systems should be configured to detect unusual authentication patterns that might indicate exploitation attempts. Security teams should also consider implementing network-based intrusion detection systems capable of identifying malformed HTTP requests targeting the vulnerable authentication mechanism. From a compliance perspective, this vulnerability aligns with CWE-121 stack-based buffer overflow classification and represents a significant concern under the ATT&CK framework's privilege escalation and execution techniques, particularly targeting industrial control systems. Organizations should conduct comprehensive inventory assessments to identify all affected devices and establish incident response procedures for potential exploitation scenarios. The vulnerability demonstrates the critical importance of input validation in embedded systems and highlights the need for robust security practices in operational technology environments where traditional cybersecurity measures may be insufficient.