CVE-2026-77946 in TEW-821DAP
Summary
by MITRE • 08/22/2026
A vulnerability was determined in TRENDnet TEW-821DAP 2.2.01b05. Affected by this vulnerability is the function uci_safe_get of the file /cgi-bin/apply_time.cgi of the component NTP Timezone Configuration Handler. Executing a manipulation of the argument system.ntp.server/system.ntp.enable_server/cameo.time.time_zone/cameo.cameo.syslog_server can lead to stack-based buffer overflow. The attack may be launched remotely. The exploit has been publicly disclosed and may be utilized.
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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 network configuration interface, specifically affecting the NTP Timezone Configuration Handler component. This handler is responsible for processing user inputs related to system time synchronization and timezone settings via the Common Gateway Interface script located at /cgi-bin/apply_time.cgi. The core of the issue lies in the uci_safe_get function, which is designed to retrieve configuration values from the Unified Configuration Interface database but fails to adequately validate or sanitize input data before passing it to lower-level system functions. This lack of rigorous boundary checking allows an attacker to supply specially crafted arguments for parameters such as system.ntp.server, system.ntp.enable_server, cameo.time.time_zone, and cameo.cameo.syslog_server. When these manipulated inputs are processed, they exceed the allocated memory buffers on the stack, resulting in a stack-based buffer overflow condition that corrupts adjacent memory locations.
From a technical perspective, this flaw is classified under CWE-121, which denotes a stack-based buffer overflow vulnerability. The mechanism of exploitation relies on the ability to overwrite critical data structures stored on the call stack, including return addresses and saved frame pointers. By carefully crafting the payload within the vulnerable arguments, an attacker can redirect the execution flow of the program to arbitrary code injected into the memory space. This type of flaw is particularly dangerous in embedded devices like wireless access points because it often bypasses standard input validation checks that are typically applied to other parts of the application logic. The presence of this vulnerability indicates a fundamental weakness in the secure coding practices employed during the development of the firmware, specifically regarding the handling of external inputs within CGI scripts that interface directly with system configuration utilities.
The operational impact of this vulnerability is severe due to its remote exploitability and public disclosure status. Since the affected component handles network time protocol configurations, it is accessible over the network without requiring prior authentication in many default or misconfigured setups, allowing for a remote code execution attack vector aligned with MITRE ATT&CK technique T1059, Command and Scripting Interpreter, specifically through local system commands executed via buffer overflow exploitation. An attacker who successfully exploits this flaw can achieve arbitrary code execution on the compromised device with the privileges of the web server process, which often runs as root or a high-privilege user in embedded Linux environments. This grants full control over the access point, enabling the attacker to pivot into the internal network, intercept traffic, install persistent malware, or use the device as part of a botnet for distributed denial-of-service attacks. The public availability of exploits significantly lowers the barrier to entry for malicious actors, increasing the likelihood of widespread automated exploitation in unpatched environments.
Mitigation strategies must prioritize immediate remediation through firmware updates provided by TRENDnet that address this specific buffer overflow issue within the uci_safe_get function and related input validation routines. In cases where patching is not immediately feasible, network segmentation should be implemented to restrict access to the management interface of the device from untrusted networks. Additionally, disabling unnecessary services such as remote NTP configuration or syslog forwarding can reduce the attack surface if these features are not strictly required for operations. Security monitoring tools should also be configured to detect anomalous traffic patterns indicative of buffer overflow attempts, although this is often challenging in encrypted management channels. Long-term resilience requires adopting secure development lifecycle practices that include static analysis and fuzzing testing focused on CGI scripts and configuration handlers to prevent similar stack-based vulnerabilities from being introduced into future firmware releases.