CVE-2026-77945 in TEW-821DAP
Summary
by MITRE • 08/22/2026
A vulnerability was found in TRENDnet TEW-821DAP 2.2.01b05. Affected is an unknown function of the file /cgi-bin/upload.cgi of the component ssi. Performing a manipulation of the argument filename results in command injection. The attack may be initiated remotely. The exploit has been made public and could be used.
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Analysis
by VulDB Data Team • 08/22/2026
The vulnerability identified in TRENDnet TEW-821DAP firmware version 2.2.01b05 represents a critical security flaw within the device's web management interface, specifically located in the server-side script /cgi-bin/upload.cgi which handles file upload operations via the ssi component. This issue is classified as a command injection vulnerability, where an attacker can manipulate specific input arguments to execute arbitrary system commands on the underlying operating system of the network appliance. The core technical flaw stems from insufficient sanitization or validation of user-supplied data passed through the filename argument during the file upload process. When the application processes this untrusted input without properly escaping special characters such as semicolons, pipes, or backticks, it inadvertently passes these commands to a shell interpreter for execution. This lack of proper input validation allows an attacker to break out of the intended context and inject malicious payloads that interact directly with the device's command line interface.
The operational impact of this vulnerability is severe due to its remote nature and the high privileges typically held by web server processes on embedded devices like wireless access points. Since the attack can be initiated remotely, a threat actor does not need physical access or prior authentication if the management interface is exposed to untrusted networks, although many such interfaces may require basic credentials which are often weak or default in IoT environments. Successful exploitation grants the attacker full control over the device's operating system, effectively compromising its confidentiality, integrity, and availability. This can lead to the installation of persistent malware, use of the device as a pivot point for lateral movement within an internal network, participation in botnets such as Mirai, or complete denial of service by crashing the firmware. The fact that public exploits exist significantly lowers the barrier to entry for attackers, increasing the likelihood of automated scanning and exploitation campaigns targeting this specific hardware model and firmware version.
From a classification perspective, this vulnerability aligns with CWE-78 Improper Neutralization of Special Elements used in an OS Command commonly known as OS Command Injection. It also maps to MITRE ATT&CK techniques related to Remote Services such as T1059 Command and Scripting Interpreter, where adversaries use scripts or commands to execute malicious actions on compromised systems. The presence of public exploits indicates that this is a mature vulnerability with established exploitation methodologies available in the wild security community tools.
Mitigation strategies for this issue primarily involve updating the firmware to a patched version released by TRENDnet if one exists, as vendor patches typically address input validation flaws through proper encoding or whitelisting of allowed characters. In cases where patching is not immediately feasible, network-level controls should be implemented to restrict access to the management interface only from trusted IP addresses using firewall rules. Additionally, changing default administrative credentials and disabling remote administration features can reduce the attack surface. Continuous monitoring for unusual outbound traffic from the device may also help in detecting potential compromise resulting from successful exploitation of this command injection flaw.