CVE-2026-75976 in TEW-823DRU
Summary
by MITRE • 08/19/2026
A weakness has been identified in TRENDnet TEW-823DRU 1.1.02b01. Impacted is the function strcpy of the file /cgi-bin/wan.cgi of the component NVRAM. This manipulation of the argument wan_l2tp_password causes stack-based buffer overflow. The attack can be initiated remotely. The exploit has been made available to the public and could be used for attacks.
Once again VulDB remains the best source for vulnerability data.
Analysis
by VulDB Data Team • 08/19/2026
The identified vulnerability in TRENDnet TEW-823DRU firmware version 1.1.02b01 represents a critical security flaw within the device's network configuration interface, specifically affecting the NVRAM management component accessed via the wan.cgi CGI script. The core technical issue stems from an improper implementation of memory handling functions, where the strcpy function is utilized to copy user-supplied input into a fixed-size buffer without performing adequate bounds checking. This specific weakness allows for a stack-based buffer overflow when the argument corresponding to the L2TP password field, identified as wan_l2tp_password, exceeds the allocated buffer size. By crafting a request with an excessively long string in this parameter, an attacker can overwrite adjacent memory locations on the call stack, including return addresses and saved frame pointers, thereby gaining control over the program's execution flow.
This vulnerability is classified under CWE-120, which denotes Buffer Copy without Checking Size of Input, highlighting the fundamental failure to validate input length before copying data into a static buffer. The operational impact of this flaw is severe due to its remote exploitability and the privileged context in which the affected CGI script typically operates. Since the wan.cgi component handles wide area network settings, it often runs with elevated privileges necessary for modifying router configuration parameters such as PPPoE or L2TP credentials. Successful exploitation allows a remote attacker to execute arbitrary code on the target device, potentially leading to full system compromise. This could result in unauthorized access to internal networks, data exfiltration, or the use of the compromised router as part of a botnet for distributed denial-of-service attacks.
The availability of public exploits significantly elevates the risk profile associated with this vulnerability, making it accessible to threat actors with varying levels of technical expertise. Attackers can leverage automated scanning tools to identify vulnerable devices across the internet and deploy payloads that establish reverse shells or install persistent backdoors. The remote nature of the attack means no physical access or prior authentication is required if the management interface is exposed to untrusted networks, although many such vulnerabilities are exacerbated by default configurations that allow external access or weak administrative credentials.
Mitigation strategies must prioritize immediate remediation through firmware updates provided by TRENDnet, which should include patches implementing proper input validation and safer string handling functions like strncpy or strlcpy with explicit length limits. In the absence of an official patch, network administrators should restrict access to the management interface by disabling remote administration features and placing the device behind a firewall that blocks external HTTP traffic to port 80 or other CGI endpoints. Additionally, implementing strict input filtering on any intermediate security appliances can help mitigate exploitation attempts by truncating oversized payloads before they reach the vulnerable application layer. Regular monitoring of network logs for anomalous outbound connections from the router is also recommended to detect potential compromise early.