Executive Summary

The vulnerability exists in the Tenda i12 router version V1.0.0.11(3862) within its HTTP handler component. Specifically, it is a path traversal flaw in the R7WebsSecurityHandler function, which is supposed to enforce access control by allowing unauthenticated access only to certain URL prefixes (like "/public/" or "/lang/").

The function checks if the beginning of a URL matches a trusted prefix using a string comparison, but it does not properly validate or canonicalize the rest of the URL. An attacker can exploit this by crafting a URL that starts with a whitelisted prefix but includes directory traversal sequences ("../") to escape the restricted directory.

For example, a URL like "/public/../system_upgrade.asp" passes the whitelist check but actually accesses a sensitive administrative page. This allows an unauthenticated remote attacker to bypass login requirements and gain direct administrative access.

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Impact Analysis

This vulnerability can have serious impacts because it allows an unauthenticated remote attacker to bypass authentication and gain full administrative access to the affected Tenda i12 router.

With this access, the attacker can manipulate router settings, potentially compromising network security, intercepting or redirecting traffic, and deploying further attacks within the network.

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Detection Guidance

This vulnerability can be detected by sending crafted HTTP GET requests that attempt to bypass authentication using path traversal sequences in the URL. Specifically, requests that start with a whitelisted prefix such as "/public/" but include directory traversal patterns like "../" to access sensitive administrative pages can indicate the presence of the vulnerability.

An example command using curl to test for this vulnerability is:

• curl -i -X GET "http://<target-ip>/public/../system_upgrade.asp"

If the response returns the administrative page content without redirecting to a login page (normally a 302 redirect), it indicates the vulnerability is present.

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Compliance Impact

This vulnerability allows unauthenticated remote attackers to bypass authentication and gain full administrative access to the Tenda i12 router. Such unauthorized access to administrative interfaces and sensitive resources can lead to unauthorized disclosure, modification, or destruction of data.

Because of this, organizations using the affected device may face challenges in maintaining compliance with common standards and regulations such as GDPR and HIPAA, which require strict access controls and protection of sensitive data.

Failure to prevent unauthorized access could result in violations of these regulations, potentially leading to legal penalties, data breaches, and loss of trust.

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Mitigation Strategies

To mitigate this vulnerability immediately, restrict remote access to the Tenda i12 router's HTTP interface to trusted networks only, such as local management networks.

Avoid exposing the router's administrative interface to the internet or untrusted networks until a patch or update is available.

Monitor network traffic for suspicious requests that attempt path traversal sequences like '/../' in URLs targeting the router.

If possible, apply any available firmware updates or patches from the vendor that address this vulnerability.

Consider using network-level protections such as firewalls or access control lists to block unauthorized HTTP requests to the device.

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