CVE-2018-5371 in DSL-2540U
Summary
by MITRE
diag_ping.cmd on D-Link DSL-2640U devices with firmware IM_1.00 and ME_1.00, and DSL-2540U devices with firmware ME_1.00, allows authenticated remote attackers to execute arbitrary OS commands via shell metacharacters in the ipaddr field of an HTTP GET request.
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Analysis
by VulDB Data Team • 12/23/2019
The vulnerability identified as CVE-2018-5371 represents a critical command injection flaw affecting D-Link DSL-2640U and DSL-2540U broadband routers. This security weakness resides within the diag_ping.cmd script component of the affected devices' firmware implementations, specifically versions IM_1.00 and ME_1.00 for the DSL-2640U and ME_1.00 for the DSL-2540U. The vulnerability manifests when an authenticated attacker submits a specially crafted HTTP GET request containing shell metacharacters within the ipaddr parameter, enabling unauthorized command execution on the underlying operating system. This flaw falls under the CWE-77 category of Command Injection, which is classified as a high-severity vulnerability in the Common Weakness Enumeration framework.
The technical exploitation of this vulnerability requires an attacker to possess valid authentication credentials for the router's administrative interface, as the vulnerability operates within the context of authenticated sessions. However, the impact remains severe since the authenticated attacker can leverage this weakness to execute arbitrary operating system commands with the privileges of the web server process. The attack vector involves crafting malicious HTTP requests that include shell metacharacters such as semicolons, ampersands, or other command chaining operators within the ipaddr field, which then gets processed by the diag_ping.cmd script without proper input sanitization or validation. This allows for complete system compromise including potential data exfiltration, lateral movement within network segments, and establishment of persistent backdoors.
The operational impact of CVE-2018-5371 extends beyond simple unauthorized command execution, as it provides attackers with full control over the affected router's functionality. This includes the ability to modify network configurations, disable security features, redirect traffic, or establish unauthorized network access points. The vulnerability affects devices deployed in both residential and small business environments where these D-Link routers are commonly used, potentially exposing entire networks to compromise. Network reconnaissance activities can be conducted through the compromised device, enabling attackers to map internal network topology and identify other vulnerable systems. From an adversarial perspective, this vulnerability aligns with ATT&CK technique T1059.001 for Command and Scripting Interpreter, and T1068 for Exploitation for Privilege Escalation, making it a significant concern for threat actors seeking persistent access to network infrastructure.
Organizations and individuals should immediately implement mitigations including firmware updates from D-Link, which address the input validation issues in the diag_ping.cmd script. Network segmentation and access control measures should be enforced to limit administrative access to these devices, while monitoring for suspicious HTTP GET requests containing unusual characters in the ipaddr parameter should be implemented. Regular security assessments and network scanning should be conducted to identify potentially affected devices, and multi-factor authentication should be enabled where available. The vulnerability demonstrates the importance of proper input validation in web applications and highlights the need for secure coding practices that prevent command injection attacks through user-supplied data. Given the widespread deployment of these router models, the vulnerability represents a significant risk to network security infrastructure and requires immediate remediation to prevent exploitation by malicious actors.