CVE-2017-8087 in Fritz!Box 7490
Summary
by MITRE
Information Leakage in PPPoE Packet Padding in AVM Fritz!Box 7490 with Firmware versions Fritz!OS 6.80 and 6.83 allows physically proximate attackers to view slices of previously transmitted packets or portions of memory via via unspecified vectors.
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Analysis
by VulDB Data Team • 01/17/2024
The vulnerability identified as CVE-2017-8087 represents a critical information disclosure flaw within the PPPoE packet handling mechanism of AVM FritzOS 6.80 and 6.83, creating a security risk that can be exploited by attackers who are physically present in the network environment. The vulnerability stems from improper handling of packet padding during PPPoE (Point-to-Point Protocol over Ethernet) communication processes, which exposes sensitive data that should remain confidential. The attack vector requires physical proximity to the device, indicating that the vulnerability is particularly concerning in environments where unauthorized physical access cannot be adequately controlled.
The technical implementation flaw occurs within the router's PPPoE packet processing routines where padding bytes are not properly managed or cleared between transmitted packets. When PPPoE packets are constructed or processed, certain memory regions may retain data from previous transmissions due to inadequate memory sanitization. This memory leakage allows an attacker with physical access to potentially recover fragments of previously transmitted data, including potentially sensitive information such as authentication credentials, network configuration details, or other confidential communication contents. The vulnerability operates at the network protocol level, specifically within the PPPoE layer of the TCP/IP stack implementation, making it particularly insidious as it can expose data that was transmitted over the network even after the original packets have been processed.
The operational impact of this vulnerability extends beyond simple information disclosure, as it can potentially enable more sophisticated attacks when combined with other exploitation techniques. An attacker who gains physical access to the device could reconstruct portions of network traffic, potentially leading to credential theft, network reconnaissance, or further exploitation of the device's services. The fact that this vulnerability affects multiple firmware versions suggests it represents a fundamental design flaw rather than a temporary coding error, making it more persistent and difficult to remediate. The attack requires physical proximity but not necessarily network access, which means that even secured networks with proper firewall configurations could be compromised if an attacker can gain physical access to the router. This creates a significant risk for enterprise environments where physical security controls may be insufficient or where devices are located in accessible areas.
The vulnerability aligns with CWE-200, which addresses "Information Exposure," and represents a specific implementation weakness in memory management during packet processing. From an ATT&CK framework perspective, this vulnerability maps to T1046 Network Service Scanning and T1566 Phishing, as it enables an attacker to gather information that could be used for more sophisticated social engineering or network reconnaissance activities. The physical access requirement places this vulnerability in the context of physical security controls and highlights the importance of securing network infrastructure at the physical layer. Mitigation strategies should focus on firmware updates from AVM, implementation of physical security controls, and network segmentation to limit the impact of potential exploitation. Organizations should also consider monitoring for unusual network behavior that might indicate packet reconstruction attempts, and ensure that all network devices are regularly updated with the latest security patches. The vulnerability underscores the critical importance of proper memory management in embedded systems and the need for comprehensive security testing of network infrastructure devices.