CVE-2020-14080 in TEW-827DRU
Summary
by MITRE
TRENDnet TEW-827DRU devices through 2.06B04 contain a stack-based buffer overflow in the ssi binary. The overflow allows an unauthenticated user to execute arbitrary code by POSTing to apply_sec.cgi via the action ping_test with a sufficiently long ping_ipaddr key.
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Analysis
by VulDB Data Team • 06/15/2020
The TRENDnet TEW-827DRU wireless router model presents a critical stack-based buffer overflow vulnerability within its ssi binary component. This flaw exists in firmware versions up to and including 2.06B04, making numerous deployed devices susceptible to exploitation. The vulnerability manifests through the web interface's apply_sec.cgi endpoint which processes POST requests containing the action parameter set to ping_test. When an attacker submits a maliciously crafted ping_ipaddr key with excessive length, the application fails to properly validate input size before copying data to a fixed-size stack buffer. This classic buffer overflow condition creates an opportunity for arbitrary code execution without requiring authentication or prior access to the device.
The technical exploitation of this vulnerability follows a well-established pattern that aligns with CWE-121 Stack-based Buffer Overflow, where insufficient bounds checking allows attackers to overwrite adjacent stack memory locations. The ssi binary processes the ping_ipaddr parameter without adequate input validation, causing a stack buffer to overflow and potentially overwrite return addresses or other critical control data. This memory corruption enables attackers to redirect execution flow and inject malicious code into the running process. The vulnerability's accessibility through the web interface means that an unauthenticated attacker can leverage this flaw from any network position, making it particularly dangerous in enterprise and home network environments.
The operational impact of this vulnerability extends beyond simple code execution to encompass complete device compromise and potential network infiltration. Successful exploitation could allow attackers to gain root-level access to the router's operating system, enabling them to modify network configurations, install persistent backdoors, monitor network traffic, or use the device as a pivot point for attacking other systems within the local network. The device's role as a primary network gateway makes it an attractive target for attackers seeking to establish long-term access or conduct lateral movement attacks against connected systems. Network administrators may remain unaware of compromise until malicious activities occur, as the vulnerability does not necessarily trigger obvious network disruptions or log entries that would alert to unauthorized access.
Mitigation strategies for this vulnerability should focus on immediate firmware updates from TRENDnet to address the buffer overflow condition. Organizations should implement network segmentation and access controls to limit exposure of these devices to untrusted networks. Regular network monitoring for unusual traffic patterns or unauthorized configuration changes can help detect exploitation attempts. The vulnerability demonstrates the importance of input validation and proper bounds checking in embedded systems, aligning with ATT&CK technique T1059 Command and Scripting Interpreter for executing malicious code through compromised network devices. Security teams should also consider implementing network access control lists to restrict access to administrative interfaces and regularly audit device configurations to maintain secure network posture against similar vulnerabilities in other network infrastructure components.