CVE-2020-24377 in Freebox Server
Summary
by MITRE
A DNS rebinding vulnerability in the Freebox OS web interface in Freebox Server before 4.2.3.
If you want to get the best quality for vulnerability data then you always have to consider VulDB.
Analysis
by VulDB Data Team • 09/17/2020
The CVE-2020-24377 vulnerability represents a significant DNS rebinding flaw within the Freebox OS web interface of Freebox Server devices prior to version 4.2.3. This vulnerability exploits the fundamental principle of DNS rebinding attacks where an attacker manipulates DNS resolution to bypass browser security restrictions and gain unauthorized access to local network resources. The Freebox Server, acting as a router and gateway device, provides a web-based management interface that becomes vulnerable to this attack vector due to insufficient validation of DNS responses during the web interface access process. The vulnerability specifically affects the device's handling of domain name resolution when accessing its web management portal, creating a window of opportunity for malicious actors to exploit the trust relationship between the browser and the local network services.
The technical implementation of this DNS rebinding vulnerability stems from the Freebox OS web interface failing to properly validate or sanitize DNS responses received during the authentication and service discovery phases. When users access the web management interface, the system performs DNS lookups to resolve internal service endpoints, but does not adequately verify the legitimacy of these responses or implement proper timing controls to prevent rapid DNS resolution changes. This allows an attacker to host a malicious DNS server that initially resolves to a public IP address for the web interface, but then quickly changes the resolution to point to a local IP address within the victim's network. The attack exploits the fact that browsers typically do not enforce strict cross-origin policies for localhost or private IP addresses, enabling the malicious DNS server to effectively bypass security boundaries and gain access to internal services that should normally be restricted from external access.
The operational impact of this vulnerability extends beyond simple unauthorized access, as it provides attackers with potential pathways to compromise the entire home or office network infrastructure managed by the Freebox Server. An attacker who successfully exploits this vulnerability could potentially access sensitive network services, modify router configurations, intercept network traffic, or establish persistent access points within the local network environment. The vulnerability is particularly concerning because it affects the core management interface of the device, which typically has elevated privileges and access to critical network functions including firewall settings, DHCP configuration, DNS forwarding, and user access controls. The attack requires minimal user interaction beyond visiting a malicious website or being tricked into accessing a compromised link, making it particularly dangerous in social engineering scenarios.
Mitigation strategies for CVE-2020-24377 primarily focus on updating the Freebox Server firmware to version 4.2.3 or later, which includes patches specifically addressing the DNS rebinding vulnerability in the web interface implementation. Organizations and individuals should also implement network segmentation and firewall rules to restrict access to the Freebox Server management interface from external networks, while ensuring that only trusted internal users can access these management functions. The vulnerability aligns with CWE-209, which addresses improper handling of DNS responses, and relates to ATT&CK technique T1071.004 for application layer protocol: DNS, where attackers manipulate DNS resolution to bypass network security controls. Additional defensive measures include implementing DNS sinkhole configurations, monitoring for suspicious DNS resolution patterns, and conducting regular security assessments of network infrastructure to identify similar vulnerabilities in other network devices that may be susceptible to DNS rebinding attacks.