CVE-2019-19941 in Centro Grande
Summary
by MITRE
Missing hostname validation in Swisscom Centro Grande before 6.16.12 allows a remote attacker to inject its local IP address as a domain entry in the DNS service of the router via crafted hostnames in DHCP requests, causing XSS.
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Analysis
by VulDB Data Team • 03/17/2020
The vulnerability identified as CVE-2019-19941 resides in the Swisscom Centro Grande router firmware version prior to 6.16.12, representing a critical security flaw in the device's DNS service implementation. This issue stems from inadequate hostname validation mechanisms that fail to properly sanitize or verify domain names submitted through DHCP requests, creating a pathway for malicious actors to exploit the system's trust model. The vulnerability specifically affects the router's handling of dynamic host configuration protocol messages where client devices request network parameters including DNS resolution capabilities.
The technical flaw manifests when a remote attacker crafts malicious DHCP requests containing specially formatted hostnames that bypass the router's hostname validation checks. These crafted hostnames can contain local IP address representations or other malicious domain entries that the router's DNS service processes without proper verification. The absence of proper input sanitization allows arbitrary hostnames to be injected into the router's DNS resolution system, effectively enabling attackers to manipulate how domain names resolve within the local network environment. This particular weakness falls under CWE-20, known as "Improper Input Validation," which directly relates to the insufficient validation of hostname data within the DHCP processing pipeline.
The operational impact of this vulnerability extends beyond simple DNS manipulation, as it creates a potential cross-site scripting (XSS) attack vector within the router's web interface. When the maliciously injected hostnames are processed by the DNS service and subsequently displayed in the router's management interface, they can execute malicious scripts in the context of the logged-in user's browser session. This creates a persistent threat where an attacker can establish a foothold within the network and potentially escalate privileges to gain deeper access to the router's administrative functions. The attack requires only remote access to the network to craft and submit the malicious DHCP requests, making it particularly dangerous for enterprise and residential networks alike.
The vulnerability aligns with several tactics outlined in the MITRE ATT&CK framework, specifically the T1059.007 technique for "Command and Scripting Interpreter: JavaScript" and T1566.001 for "Phishing: Spearphishing Attachment." Attackers can leverage this weakness to inject malicious JavaScript code through the DNS injection mechanism, potentially redirecting users to malicious sites or executing persistent malware. The exploitation process demonstrates the principle of privilege escalation through service manipulation, where a low-privilege network attacker can compromise the router's DNS service and subsequently access the web interface with elevated privileges.
Organizations should implement immediate mitigations including firmware updates to version 6.16.12 or later, which addresses the hostname validation flaw through enhanced input sanitization. Network administrators should also consider implementing DHCP snooping and dynamic ARP inspection to prevent unauthorized DHCP server activities, while monitoring for unusual DHCP request patterns that may indicate exploitation attempts. The vulnerability highlights the importance of proper input validation in network services and demonstrates how seemingly minor security gaps in DHCP processing can create significant attack surfaces for sophisticated adversaries. Additional security controls such as network segmentation and regular security audits of network infrastructure can help prevent exploitation of similar vulnerabilities in other network devices.