CVE-2019-20747 in D6100
Summary
by MITRE
Certain NETGEAR devices are affected by a stack-based buffer overflow by an authenticated user. This affects D6100 before 1.0.0.58, D7800 before 1.0.1.40, R7500v2 before 1.0.3.34, R7800 before 1.0.2.52, R8900 before 1.0.4.2, R9000 before 1.0.3.16, RAX120 before 1.0.0.74, RBK20 before 2.3.0.22, RBR20 before 2.3.0.22, RBS20 before 2.3.0.22, RBK50 before 2.3.0.22, RBR50 before 2.3.0.22, RBS50 before 2.3.0.22, RBK40 before 2.3.0.22, RBS40 before 2.3.0.22, SRK60 before 2.2.0.64, SRR60 before 2.2.0.64, SRS60 before 2.2.0.64, WNDR3700v4 before 1.0.2.102, WNDR4300 before 1.0.2.104, WNDR4300v2 before 1.0.0.56, WNDR4500v3 before 1.0.0.56, and WNR2000v5 before 1.0.0.66.
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Analysis
by VulDB Data Team • 05/31/2024
This vulnerability represents a critical stack-based buffer overflow condition that affects multiple NETGEAR wireless routers and networking devices, creating a significant security risk for network infrastructure. The flaw occurs within the web management interface of these devices, specifically when processing user-supplied input through HTTP requests. An authenticated attacker who has already gained access to the device's administrative interface can exploit this vulnerability to execute arbitrary code on the affected systems. The vulnerability is particularly concerning because it requires only authentication, which is often readily available through default credentials or compromised administrative accounts. The affected models span several product lines including the D6100, D7800, R7500v2, R7800, R8900, R9000, and various RAX, RBK, RBR, RBS, SRK, SRR, and SRS series routers, indicating a widespread issue across NETGEAR's product portfolio.
The technical implementation of this buffer overflow occurs when the device processes certain parameters in HTTP requests sent to the web management interface. The flaw stems from insufficient bounds checking on user input, allowing an attacker to overflow a fixed-size stack buffer with malicious data. When the vulnerable code attempts to copy user-supplied data into a buffer that is too small to accommodate the input, the excess data overflows into adjacent memory locations, potentially overwriting critical program control data such as return addresses or function pointers. This memory corruption can be exploited to redirect program execution flow and execute arbitrary code with the privileges of the web server process, typically running with elevated system privileges. The vulnerability is classified under CWE-121 as a stack-based buffer overflow, which is a well-documented and dangerous class of memory corruption vulnerabilities that has been extensively studied in security research and has been mapped to various ATT&CK techniques including T1059 for command and scripting interpreter and T1068 for exploit for privilege escalation.
The operational impact of this vulnerability extends beyond simple code execution, as it can enable complete system compromise and persistent access to the affected networks. An attacker who successfully exploits this vulnerability can gain full administrative control over the affected device, allowing them to modify network configurations, install malicious firmware, create backdoors, or use the device as a pivot point to attack other systems within the network. The affected devices typically serve as primary network gateways, making them attractive targets for attackers seeking to establish long-term access or to use the devices as command and control points for broader network attacks. Additionally, the vulnerability's presence in multiple device models suggests that attackers could potentially target entire network infrastructures simultaneously, depending on the network topology and device deployment patterns. The fact that these devices are often deployed in residential and small business environments where default credentials are commonly left unchanged makes this vulnerability particularly dangerous, as it can be exploited with minimal reconnaissance effort.
Mitigation strategies for this vulnerability should include immediate firmware updates from NETGEAR, which are available for all affected models and address the buffer overflow through proper input validation and bounds checking. Network administrators should also implement strict access controls and authentication measures, including changing default credentials, implementing multi-factor authentication, and restricting access to the web management interfaces to trusted IP addresses only. Regular network monitoring and intrusion detection systems should be configured to detect unusual traffic patterns or attempts to access administrative interfaces. Organizations should also consider network segmentation to limit the potential impact of a successful exploitation, ensuring that compromised devices cannot easily access critical network resources. The vulnerability demonstrates the importance of proper input validation in web applications and highlights the need for security testing during the development lifecycle, particularly for embedded systems that handle user input through web interfaces. Security professionals should also consider implementing network access controls and monitoring for unusual administrative activity that could indicate exploitation attempts. Given the widespread nature of the affected devices, organizations should conduct comprehensive inventory audits to identify all potentially vulnerable systems and prioritize remediation efforts based on risk assessment and network criticality.