CVE-2018-15517 in Central WiFiManager CWM-100
Summary
by MITRE
The MailConnect feature on D-Link Central WiFiManager CWM-100 1.03 r0098 devices is intended to check a connection to an SMTP server but actually allows outbound TCP to any port on any IP address, leading to SSRF, as demonstrated by an index.php/System/MailConnect/host/127.0.0.1/port/22/secure/ URI.
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Analysis
by VulDB Data Team • 06/23/2024
The vulnerability CVE-2018-15517 affects the D-Link Central WiFiManager CWM-100 device running firmware version 1.03 r0098 and represents a significant security flaw in the MailConnect feature implementation. This issue stems from improper input validation and access control mechanisms within the device's web interface, where the intended functionality of checking SMTP server connectivity has been subverted to allow unrestricted outbound network access. The vulnerability manifests through a specific URI pattern that demonstrates how attackers can bypass intended network restrictions to access any TCP port on any IP address, effectively creating a server-side request forgery vector that can be exploited to probe internal networks and systems.
The technical flaw resides in the device's handling of the MailConnect functionality, which should only permit connections to standard SMTP ports such as 25, 465, or 587 but instead allows arbitrary port scanning and connection attempts. When a user accesses the URI structure index.php/System/MailConnect/host/127.0.0.1/port/22/secure/, the device fails to validate the destination parameters and executes the connection attempt without proper authorization checks. This behavior represents a classic case of insufficient input validation and improper access control, with the vulnerability mapping to CWE-918 Server-Side Request Forgery and CWE-284 Improper Access Control. The flaw essentially transforms the device from a simple network management tool into a potential reconnaissance platform for attackers seeking to map internal network topologies and identify vulnerable services.
The operational impact of this vulnerability extends beyond simple information disclosure, as it enables attackers to perform network reconnaissance and potentially identify internal services that would otherwise remain hidden from external view. The ability to connect to port 22 on localhost demonstrates how an attacker can use this vulnerability to probe for SSH services, while the unrestricted port access capability allows for broader scanning operations against internal systems. This represents a significant risk to organizations using these devices, as they may unknowingly provide attackers with a method to bypass network segmentation controls and gain insights into internal network architecture. The vulnerability can be exploited to identify running services, potentially discover misconfigured systems, and map internal network topology, making it a valuable tool for attackers planning more sophisticated attacks.
Mitigation strategies for CVE-2018-15517 should prioritize immediate firmware updates from D-Link to address the underlying implementation flaw, as the manufacturer likely released a patched version to correct the improper access control mechanisms. Network segmentation and firewall rules should be implemented to restrict outbound connections from the device to prevent unauthorized access to internal systems, while monitoring systems should be deployed to detect unusual outbound connection patterns. Organizations should also consider disabling the MailConnect feature entirely if it is not required for business operations, as this eliminates the attack surface associated with the vulnerability. The implementation of web application firewalls and input validation controls can provide additional protection against similar issues in other applications, aligning with ATT&CK technique T1106 Network Service Scanning and T1071.3 Application Layer Protocol. Regular security assessments and network monitoring should be conducted to identify any potential exploitation attempts, while security awareness training for administrators can help prevent accidental activation of vulnerable features through improper configuration practices.