Asus Router AsusWRT-Merlin router/httpd/web.c ej_update_variables action_script memory corruption

Summaryinfo

A vulnerability, which was classified as critical, has been found in Asus Router. This impacts the function ej_update_variables of the file router/httpd/web.c of the component AsusWRT-Merlin. Performing a manipulation of the argument action_script as part of Variable results in memory corruption. This vulnerability is known as CVE-2018-5721. Remote exploitation of the attack is possible. No exploit is available.

Detailsinfo

A vulnerability, which was classified as critical, was found in Asus Router (Router Operating System) (affected version unknown). This affects the function ej_update_variables of the file router/httpd/web.c of the component AsusWRT-Merlin. The manipulation of the argument action_script as part of a Variable leads to a memory corruption vulnerability. CWE is classifying the issue as CWE-119. The product performs operations on a memory buffer, but it can read from or write to a memory location that is outside of the intended boundary of the buffer. This is going to have an impact on confidentiality, integrity, and availability. The summary by CVE is:

Stack-based buffer overflow in the ej_update_variables function in router/httpd/web.c on ASUS routers (when using software from https://github.com/RMerl/asuswrt-merlin) allows web authenticated attackers to execute code via a request that updates a setting. In ej_update_variables, the length of the variable action_script is not checked, as long as it includes a "_wan_if" substring.

The bug was discovered 01/16/2018. The weakness was published 01/17/2018 (Website). The advisory is shared at w0lfzhang.com. This vulnerability is uniquely identified as CVE-2018-5721 since 01/16/2018. The exploitability is told to be easy. It is possible to initiate the attack remotely. The successful exploitation needs a authentication. Technical details are known, but no exploit is available.

The vulnerability was handled as a non-public zero-day exploit for at least 1 days. During that time the estimated underground price was around $0-$5k.

There is no information about possible countermeasures known. It may be suggested to replace the affected object with an alternative product.

Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

Productinfo

Type

• Router Operating System

Vendor

• Asus

Name

• Router

License

• commercial

Website

• Vendor: https://www.asus.com/

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Entryinfo

Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

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