CVE-2018-20872 in DrayTek
Summary
by MITRE
DrayTek routers before 2018-05-23 allow CSRF attacks to change DNS or DHCP settings, a related issue to CVE-2017-11649.
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Analysis
by VulDB Data Team • 11/14/2023
This vulnerability affects DrayTek routers prior to the 2018-05-23 firmware update and represents a cross-site request forgery flaw that enables unauthorized modification of critical network configuration parameters. The vulnerability specifically targets DNS and DHCP settings within the router's web management interface, allowing attackers to manipulate these essential network services without proper authentication. The issue is classified as a CSRF vulnerability under CWE-352, which occurs when a web application fails to verify the origin of requests, enabling malicious actors to perform actions on behalf of authenticated users. The vulnerability is particularly concerning because it directly impacts fundamental network operations, potentially allowing attackers to redirect traffic through malicious DNS servers or disrupt network services via DHCP configuration changes.
The technical implementation of this flaw stems from inadequate request validation mechanisms within the router's web interface. When administrators access the router's management console, the system should verify that requests originate from legitimate sources and contain proper authentication tokens. However, in vulnerable versions, the router fails to implement sufficient anti-CSRF measures, particularly in the DNS and DHCP configuration endpoints. This allows attackers to craft malicious web pages or send specially crafted requests that, when executed by an authenticated user, modify network settings without the user's knowledge or consent. The vulnerability specifically relates to CVE-2017-11649, indicating a pattern of similar issues in the same vendor's products, suggesting systematic weaknesses in the CSRF protection mechanisms across multiple firmware versions.
The operational impact of this vulnerability extends beyond simple configuration changes, potentially enabling sophisticated attack scenarios that compromise network security and availability. An attacker who successfully exploits this vulnerability could redirect all network traffic through malicious DNS servers, enabling man-in-the-middle attacks, DNS poisoning, or redirection to phishing sites. The DHCP modification capability could lead to network disruption by assigning incorrect IP addresses, causing connectivity issues for legitimate users, or enabling attackers to place themselves in the network traffic path. This vulnerability directly impacts the CIA triad by compromising confidentiality through DNS manipulation, integrity through unauthorized configuration changes, and availability through potential network disruption. The attack vector requires user interaction, typically through clicking malicious links or visiting compromised websites, making it particularly dangerous in environments where users may not be security-aware.
Mitigation strategies for this vulnerability should focus on immediate firmware updates to versions released after 2018-05-23, which contain proper CSRF protection mechanisms. Network administrators should also implement additional security controls such as disabling unnecessary web management interfaces, restricting access to router management consoles to trusted IP ranges, and employing network monitoring to detect unauthorized configuration changes. The implementation of proper CSRF tokens and origin validation should be enforced across all web interfaces, following established security frameworks such as the OWASP CSRF Prevention Cheat Sheet. Organizations should also consider network segmentation and the principle of least privilege to limit the potential impact of successful exploitation. This vulnerability highlights the importance of maintaining up-to-date firmware and implementing proper security controls in network infrastructure devices, as outlined in NIST SP 800-125 and other cybersecurity frameworks that emphasize the critical nature of securing network management interfaces and the potential for CSRF attacks to compromise fundamental network services.