CVE-2018-14559 in AC7
Summary
by MITRE
An issue was discovered on Tenda AC7 devices with firmware through V15.03.06.44_CN(AC7), AC9 devices with firmware through V15.03.05.19(6318)_CN(AC9), and AC10 devices with firmware through V15.03.06.23_CN(AC10). A buffer overflow vulnerability exists in the router's web server (httpd). When processing the list parameters for a post request, the value is directly written with sprintf to a local variable placed on the stack, which overrides the return address of the function, causing a buffer overflow.
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Analysis
by VulDB Data Team • 09/07/2023
The vulnerability identified as CVE-2018-14559 represents a critical buffer overflow flaw affecting Tenda wireless routers including AC7 AC9 and AC10 models with specific firmware versions. This issue resides within the web server component known as httpd which processes incoming post requests from web clients. The vulnerability manifests when the router's web server handles the list parameters contained within post requests, creating a dangerous condition that can be exploited by remote attackers to gain unauthorized control over the affected devices. The flaw specifically impacts firmware versions through V15.03.06.44_CN(AC7) V15.03.05.19(6318)_CN(AC9) and V15.03.06.23_CN(AC10), indicating a widespread issue affecting multiple router models within the Tenda product line.
The technical mechanism behind this vulnerability involves a classic stack-based buffer overflow condition that occurs during the processing of HTTP post requests. When the httpd web server receives a post request containing list parameters, it directly employs the sprintf function to write data into a local stack variable without proper bounds checking or validation. This improper handling allows an attacker to supply input data that exceeds the allocated buffer size, causing the excess data to overwrite adjacent memory locations including the function's return address on the stack. This memory corruption fundamentally compromises the program's execution flow and enables arbitrary code execution capabilities. The vulnerability aligns with CWE-121 which describes stack-based buffer overflow conditions where insufficient bounds checking permits data to overwrite adjacent stack memory, and specifically maps to CWE-787 which addresses out-of-bounds write conditions in stack memory.
The operational impact of this vulnerability extends beyond simple denial of service scenarios to encompass full system compromise and potential network infiltration. Remote attackers can exploit this buffer overflow to execute arbitrary code on the affected routers, potentially gaining root access to the device's operating system. This access level allows attackers to modify router configurations, install malicious software, redirect network traffic, or establish persistent backdoors for future access. The implications are particularly severe because routers serve as central network infrastructure components, making successful exploitation capable of compromising entire local networks. Attackers could leverage this vulnerability to perform man-in-the-middle attacks, monitor network traffic, or use the compromised devices as launching points for broader network attacks against connected systems. The vulnerability's remote exploitability means that attackers do not require physical access to the devices, making it particularly dangerous for enterprise and home users alike.
Mitigation strategies for CVE-2018-14559 should prioritize immediate firmware updates from Tenda to address the underlying buffer overflow condition. Network administrators should implement network segmentation and access controls to limit potential attack vectors and reduce the impact of successful exploitation. Monitoring network traffic for unusual patterns or malicious requests targeting the affected routers can help detect exploitation attempts. The vulnerability demonstrates the importance of input validation and bounds checking in network services, aligning with ATT&CK technique T1059.007 which covers command and scripting interpreter execution. Organizations should also consider implementing network-based intrusion detection systems that can identify and block suspicious post request patterns targeting web servers. Additionally, regular security assessments of network infrastructure components and maintaining up-to-date security patches form essential defensive measures against similar vulnerabilities in embedded network devices. The vulnerability serves as a reminder of the critical need for secure coding practices in embedded systems and the importance of proper memory management in network service implementations.