Executive Summary

This vulnerability is a buffer overflow in the firmware update process of the TRENDnet TEW-821DAP device, specifically in firmware version 1.12B01.

It occurs in the function auto_update_firmware, where the new firmware filename (stored in the variable str) is copied into a fixed-size array without checking the length. Because the copy uses strcpy without size constraints, an attacker can provide a filename longer than 1163 bytes, causing the buffer to overflow.

This overflow can overwrite memory beyond the buffer, potentially leading to denial of service or other memory manipulation attacks.

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Impact Analysis

An attacker can remotely exploit this vulnerability by sending a specially crafted firmware filename that exceeds the buffer size.

This can cause a buffer overflow, which may lead to denial of service by crashing the device or potentially allow the attacker to manipulate memory in unintended ways.

However, this vulnerability only affects hardware version v1.xR of the device, which has been end-of-life for 8 years and is no longer supported or sold by the vendor.

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Detection Guidance

This vulnerability involves a buffer overflow in the auto_update_firmware function triggered by a specially crafted firmware filename longer than 1163 bytes.

Detection can focus on monitoring network traffic or device logs for unusually long firmware update requests or filenames exceeding typical length limits.

Since the vulnerability is triggered by a long filename in the firmware update process, commands or scripts that inspect firmware update requests or logs for filenames longer than 1163 bytes could help detect attempts to exploit this issue.

• Use packet capture tools (e.g., tcpdump or Wireshark) to monitor network traffic to the device for firmware update requests with unusually long filename parameters.
• On the device or its management interface, check logs for firmware update attempts and filter for filenames longer than expected (e.g., > 1000 bytes).
• Example tcpdump command to capture firmware update traffic (adjust interface and port as needed): tcpdump -i eth0 -A 'tcp port 80 or tcp port 443' | grep -E '.{1000,}'

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Mitigation Strategies

Immediate mitigation steps include preventing exposure of the vulnerable device to untrusted networks since the vulnerability can be exploited remotely.

Because the affected product (TRENDnet TEW-821DAP v1.xR) is end-of-life and no longer supported, no official firmware patches are available.

• Isolate the device from the internet and untrusted networks to reduce the attack surface.
• Disable or restrict remote firmware update functionality if possible.
• Monitor network traffic for suspicious firmware update attempts as a detection measure.
• Consider replacing the device with a supported model that receives security updates.

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Compliance Impact

The provided information does not specify any direct impact of this vulnerability on compliance with common standards and regulations such as GDPR or HIPAA.

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