CVE-2019-20748 in D7800
Summary
by MITRE
Certain NETGEAR devices are affected by a stack-based buffer overflow by an authenticated user. This affects D7800 before 1.0.1.44, R7500v2 before 1.0.3.38, R7800 before 1.0.2.52, RBK20 before 2.3.0.28, RBR20 before 2.3.0.28, RBS20 before 2.3.0.28, RBK40 before 2.3.0.28, RBS40 before 2.3.0.28, RBK50 before 2.3.0.32, RBR50 before 2.3.0.32, and RBS50 before 2.3.0.32.
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Analysis
by VulDB Data Team • 05/31/2024
This vulnerability represents a critical stack-based buffer overflow flaw that affects multiple NETGEAR router models within the consumer and small office networking segment. The issue stems from insufficient input validation within the device's web interface management system, where authenticated users can exploit a programming error to overwrite adjacent memory locations on the stack. The vulnerability is particularly concerning because it requires only authentication to the device's administrative interface, which is typically accessible to users with legitimate administrative credentials. This means that an attacker who has gained access to a valid user account or has previously compromised administrative credentials can leverage this flaw to execute arbitrary code on the affected devices. The affected models include a range of routers from the D7800, R7500v2, R7800, and various RBK/RBR/RBS series, all of which share a common codebase that contains this exploitable buffer overflow condition. The specific version ranges indicate that firmware updates released after the mentioned build numbers should contain fixes for this vulnerability, making it a clear target for patch management initiatives.
The technical implementation of this buffer overflow occurs when the device processes user-supplied input through the web administration interface without proper bounds checking. When an authenticated user submits specially crafted data to a vulnerable parameter, the application fails to validate the input length before copying it into a fixed-size stack buffer. This allows an attacker to overflow the buffer and overwrite adjacent memory locations including return addresses, function pointers, and other critical control data. The vulnerability is classified as a CWE-121 stack-based buffer overflow, which is a well-documented weakness in software development practices that has been consistently exploited in network device firmware. The attack vector requires network access to the device's web interface, typically port 80 or 443, and authentication credentials to access the administrative functions. This aligns with ATT&CK technique T1078 for valid accounts and T1210 for exploitation of remote services, making it a prime target for both insider threats and credential compromise scenarios.
The operational impact of this vulnerability extends beyond simple code execution, as it can enable complete device compromise and potential network infiltration. An attacker who successfully exploits this vulnerability can gain full administrative control over the affected router, potentially allowing them to modify network configurations, redirect traffic, install malicious firmware, or establish persistent backdoors. The compromised device could then serve as a pivot point for attacking other devices within the local network, or as a command and control node for broader network operations. Additionally, the router's role as a network gateway means that such an attack could provide attackers with access to internal network resources that would otherwise be protected by firewall rules. The vulnerability affects devices that are commonly deployed in residential and small business environments, where network security awareness may be limited, making these devices particularly attractive targets for exploitation. The widespread deployment of these affected models across different geographical regions and network environments amplifies the potential impact of this vulnerability.
Mitigation strategies for this vulnerability should focus on immediate firmware updates from NETGEAR, as the vendor has released patches addressing the specific buffer overflow condition. Network administrators should prioritize updating all affected devices to the latest firmware versions, particularly those with known exposure to untrusted networks or users. The authentication requirements mean that organizations should implement strict access controls and monitoring of administrative account usage, as this vulnerability could be exploited by insiders or through credential compromise. Security teams should deploy network monitoring tools to detect unusual traffic patterns or attempts to access administrative interfaces, particularly from unexpected sources or during non-business hours. Additional defensive measures include implementing network segmentation to limit the impact of a successful compromise, deploying intrusion detection systems to monitor for exploitation attempts, and establishing robust credential management policies that include regular password changes and multi-factor authentication for administrative access. The vulnerability also underscores the importance of firmware security assessments and regular security audits of network infrastructure components, as similar issues may exist in other network device firmware that has not yet been identified or patched.