Pierluigi Paganini January 18, 2023

A couple of critical vulnerabilities have been discovered in Netcomm rourers, experts warn of their potential exploitation in the wild.

The vulnerabilities discovered in the Netcomm routers are a a stack based buffer overflow and an authentication bypass, respectively tracked as CVE-2022-4873 and CVE-2022-4874.

Both issues impact the Netcomm router models NF20MESH, NF20, and NL1902 running software versions earlier than R6B035.

Below are the descriptions for both issues:

CVE-2022-4873 – Authentication bypass in Netcomm router models NF20MESH, NF20, and NL1902 allows an unauthenticated user to access content. In order to serve static content, the application performs a check for the existence of specific characters in the URL (.css, .png etc). If it exists, it performs a “fake login” to give the request an active session to load the file and not redirect to the login page.

CVE-2022-4874 – Authentication bypass in Netcomm router models NF20MESH, NF20, and NL1902 allows an unauthenticated user to access content. In order to serve static content, the application performs a check for the existence of specific characters in the URL (.css, .png etc). If it exists, it performs a “fake login” to give the request an active session to load the file and not redirect to the login page.

The CERT Coordination Center (CERT/CC) also published an advisory to warn of attacks chaining the two issues to achieve remote code execution on vulnerable systems.

“Netcomm router models NF20MESH, NF20, and NL1902 running software versions earlier than R6B035 contain two vulnerabilities.” reads the advisory. “The two vulnerabilities, when chained together, permit a remote, unauthenticated attacker to execute arbitrary code.”

The advisory pointed out that once the attacker has obtained unauthorized access to affected devices, he can use those entry points to gain access to other systems on the network or compromise the availability, integrity, or confidentiality of data being transmitted from the internal network.

The flaw was discovered by Brendan Scarvell who also published PoC to show how to chain the two vulnerabilities to achieve unauthenticated remote code execution.

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Pierluigi Paganini

(SecurityAffairs – hacking, Netcomm)

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