New Netcomm router models NF20MESH, NF20, and NL1902 vulnerabilities

guest · Jan 17, 2023

Vulnerability Note VU#986018
Original Release Date: 2023-01-17 | Last Revised: 2023-01-17

Overview
Netcomm router models NF20MESH, NF20, and NL1902 running software versions earlier than R6B035 contain two vulnerabilities. The first is an authentication bypass vulnerability that allows an unauthenticated user to access content from both inside and outside the network. The second is a stack-based buffer overflow that allows an instruction pointer to be overwritten on the stack, thereby crashing the application at a known location. The two vulnerabilities, when chained together, permit a remote, unauthenticated attacker to execute arbitrary code.
Description
Netcomm router models NF20MESH, NF20, and NL1902 running software versions earlier than R6B035 may contain two vulnerabilities:
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CVE-2022-4873 A stack based buffer overflow affects the sessionKey parameter. By providing a specific number of bytes, the instruction pointer is able to be overwritten on the stack and crashes the application at a known location.

CVE-2022-4874 Authentication bypass 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.
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The tested models that were impacted are Netcomm routers using a Broadcom chipset that had third-party code added by Shenzhen Gongjin Electronics. The third-party code introduced the vulnerabilities. These routers are deployed by residential internet service providers.
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New Netcomm router models NF20MESH, NF20, and NL1902 vulnerabilities

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New Netcomm router models NF20MESH, NF20, and NL1902 vulnerabilities

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