Executive Summary

The TOTOlink A3600R router, firmware version V5.9c.4959, has a buffer overflow vulnerability in the setAppEasyWizardConfig interface within the /lib/cste_modules/app.so library.

This vulnerability occurs because the rootSsid parameter is not properly validated for length before being used in a sprintf call that appends the string "_5G" to it.

Since the buffer receiving this data is fixed at 32 bytes and sprintf does not check bounds, if the rootSsid plus the suffix exceeds this size, it causes a buffer overflow.

This overflow can overwrite adjacent stack memory, potentially causing the device to crash or allowing an attacker to execute arbitrary code remotely.

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Impact Analysis

This vulnerability can impact you by allowing remote attackers to exploit the rootSsid parameter to trigger a buffer overflow on the affected router.

The consequences include denial of service, where the device may crash or become unresponsive, and in more severe cases, arbitrary code execution, which could let attackers take control of the device.

Such control could be used to manipulate network traffic, compromise connected devices, or use the router as a foothold for further attacks.

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Detection Guidance

This vulnerability can be detected by monitoring HTTP requests sent to the setAppEasyWizardConfig interface on the TOTOlink A3600R router. Specifically, look for requests that include the rootSsid parameter with a length exceeding 29 characters (since the buffer is 32 bytes and the suffix '_5G' adds 3 bytes). Such requests may trigger the buffer overflow.

You can use network traffic analysis tools like tcpdump or Wireshark to capture HTTP requests to the router and filter for suspicious rootSsid parameter lengths.

• Use tcpdump to capture HTTP traffic to the router's IP on port 80: tcpdump -i <interface> host <router_ip> and port 80 -w capture.pcap
• Analyze the capture with Wireshark, filtering HTTP requests to the setAppEasyWizardConfig endpoint and inspecting the rootSsid parameter length.
• Alternatively, use command-line tools like curl or wget to send crafted requests with long rootSsid values to test if the device is vulnerable.

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Mitigation Strategies

Immediate mitigation steps include restricting access to the setAppEasyWizardConfig interface to trusted networks or devices only, to prevent remote exploitation.

Additionally, monitor and block HTTP requests containing unusually long rootSsid parameters that could trigger the buffer overflow.

If possible, update the router firmware to a version that addresses this vulnerability or apply vendor-provided patches.

As a temporary measure, consider disabling the vulnerable interface or related services if they are not essential.

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