CVE-2026-76590 in TEW-755AP
Summary
by MITRE • 08/19/2026
A vulnerability was identified in TRENDnet TEW-755AP up to 20260702. Affected by this issue is some unknown functionality of the file /cgi-bin/wan.cgi of the component ssi. Such manipulation of the argument cameo.wan.wan_pppoe_password_00 leads to stack-based buffer overflow. The attack can be executed remotely. The exploit is publicly available and might be used.
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Analysis
by VulDB Data Team • 08/20/2026
The identified vulnerability in TRENDnet TEW-755AP firmware versions up to 20260702 represents a critical security flaw within the device's web management interface, specifically affecting the ssi component responsible for processing server-side includes. The root cause lies in improper input validation and boundary checking within the /cgi-bin/wan.cgi script when handling the argument cameo.wan.wan_pppoe_password_00. This specific parameter is intended to accept PPPoE password credentials during network configuration, but the underlying C code fails to enforce strict length limits on the incoming data string. Consequently, providing a payload that exceeds the allocated stack buffer size results in a classic stack-based buffer overflow condition.
From a technical perspective, this memory corruption vulnerability allows an attacker to overwrite adjacent memory locations on the call stack, including return addresses and saved frame pointers. By carefully crafting the input data, it is possible to redirect program execution flow to arbitrary code injected into the same process space or referenced via shellcode embedded in the overflowed buffer. Since the vulnerable CGI script typically runs with elevated privileges necessary for router configuration changes, successful exploitation grants the attacker full control over the device's operating system. This aligns directly with CWE-120, which classifies buffer copies without checking size limits as a fundamental memory safety error common in C and C++ applications lacking modern protections like stack canaries or ASLR enforcement.
The operational impact of this vulnerability is severe due to its remote exploitability over the network interface. An unauthenticated attacker who has network access to the management port, or potentially even through exposed WAN interfaces if default configurations are retained, can execute arbitrary commands without prior authentication in many deployment scenarios where basic CGI endpoints remain accessible. The fact that a public exploit exists significantly lowers the barrier for entry, enabling automated scanning tools and opportunistic attackers to compromise devices at scale. This capability facilitates not only local device takeover but also potential pivoting into internal networks if the router serves as a gateway, leading to data exfiltration, lateral movement, or integration into botnets such as Mirai variants that target IoT infrastructure.
This vulnerability maps closely to MITRE ATT&CK techniques related to initial access and execution on networked devices. Specifically, it relates to exploitation of remote services for command execution, often categorized under T1059 in the context of script interpretation or direct system commands via CGI interfaces. The lack of input sanitization also reflects weaknesses associated with CWE-20 improper input validation, which serves as a precursor condition allowing subsequent memory corruption attacks. Organizations relying on this hardware model face significant risk given the age of the firmware and the availability of ready-made exploits in public repositories.
Mitigation strategies must prioritize immediate isolation or decommissioning if possible, as vendor support for older TRENDnet models may be limited. If continued operation is necessary, administrators should ensure that remote management interfaces are disabled unless absolutely required, restricting access to local network segments only where feasible. Implementing strict firewall rules to block external traffic from reaching the CGI endpoints can provide a layer of defense in depth while patching efforts continue. Additionally, enabling any available firmware updates released after version 20260702 is critical if they address this specific buffer overflow issue. Network monitoring solutions should be configured to detect anomalous HTTP POST requests with unusually large payloads targeting the /cgi-bin/wan.cgi endpoint, which may indicate active exploitation attempts in real-time.