CVE-2020-24375 in Server
Summary
by MITRE • 10/20/2020
A DNS rebinding vulnerability in the UPnP MediaServer implementation in Freebox Server before 4.2.3.
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Analysis
by VulDB Data Team • 11/21/2020
The CVE-2020-24375 vulnerability represents a significant security flaw in the UPnP MediaServer implementation of Freebox Server devices, specifically affecting versions prior to 4.2.3. This vulnerability exploits a DNS rebinding attack vector that allows remote attackers to bypass security restrictions and gain unauthorized access to the device's internal network services. The flaw exists within the Universal Plug and Play protocol implementation that governs how devices discover and communicate with each other on local networks, particularly in media streaming scenarios where the UPnP MediaServer component handles content delivery and device control functions.
The technical root cause of this vulnerability stems from insufficient validation of DNS responses within the UPnP MediaServer implementation, creating an opportunity for attackers to manipulate domain name resolution during the device discovery process. When a device attempts to establish connections through UPnP protocols, the vulnerable implementation fails to properly verify the legitimacy of DNS responses, allowing malicious actors to redirect traffic to internal network services that should remain protected from external access. This represents a classic DNS rebinding vulnerability pattern where the attacker leverages the time gap between DNS resolution and connection establishment to gain access to restricted resources.
The operational impact of this vulnerability extends beyond simple unauthorized access, as it enables attackers to potentially compromise the entire local network ecosystem that the Freebox Server serves as a gateway for. An attacker could exploit this vulnerability to access internal network devices, intercept communications, or even escalate privileges to gain control over the entire router infrastructure. The attack surface is particularly concerning given that UPnP implementations are commonly used for media streaming and device discovery, making them attractive targets for exploitation. This vulnerability aligns with CWE-209, which addresses improper handling of DNS responses, and specifically relates to the broader category of DNS rebinding attacks that have been documented in various network protocols.
Mitigation strategies for CVE-2020-24375 require immediate firmware updates to version 4.2.3 or later, which contain patches addressing the DNS validation issues within the UPnP MediaServer implementation. Network administrators should also implement additional security controls such as disabling UPnP functionality when not actively needed, configuring proper firewall rules to restrict external access to UPnP ports, and monitoring network traffic for suspicious DNS resolution patterns. The vulnerability demonstrates the importance of secure DNS handling in network protocols and aligns with ATT&CK technique T1071.004, which covers DNS tunneling and manipulation techniques. Organizations should also consider implementing network segmentation strategies to limit the potential impact of such vulnerabilities and maintain updated inventories of all UPnP-enabled devices within their network infrastructure.