Update: Now VPN Mentor has been released a user-friendly patch for affected users who can provide their WebUI URL of the router and run the script that will perform further patch operation.

Critical Remote code execution vulnerability discovered in Fiber based GPON home router allows attack could compromise the entire network and bypass all authentication.

GPON is one of the widely used internet and the highest speed, longest life, lowest cost network infrastructure available in the market. Offering a genuine future‐proof access network with flexibility and upgrade capability well into the future.

This vulnerability can be exploited by just modifying the URL in the browser’s address bar and this bug allows let anyone bypass the router’s login page.

There is 2 critical vulnerability involved in this flaw and those combined 2 (CVE-2018-10561 & CVE-2018-10562) vulnerabilities allow attacker could take over and gain complete control the device and the network.

• CVE-2018-10561 –a way to bypass all authentication on the devices
• (CVE-2018-10562- command injection vulnerability to execute commands on the device

Mainly this flaw exploits the authentication mechanism using first vulnerability which leads to attack bypass all the authentication.

Bypass Router Using Simple Trick

Primary flaw found in HTTP servers that usually check the specific path when performing the authentication process which allows bypassing authentication on any endpoint system with a simple trick.

An attack can bypass the endpoint by just adding  ?images/ to the URL which works on both HTML pages and GponForm/.

/menu.html?images/
or
/GponForm/diag_FORM?images/

According to vpnmentor, While looking through the device functionalities, we noticed the diagnostic endpoint contained the ping and traceroute commands. It didn’t take much to figure out that the commands can be injected by the host parameter.

Since the router saves ping results in /tmp and transmits it to the user when the user revisits /diag.html, it’s quite simple to execute commands and retrieve their output with the authentication bypass vulnerability.

you can see the video that demonstrates the exploitation of the critical RCE flaw.

Researchers have tested many of the GPON routers and they find the same flaw in so many routers.

Also, they search in shodan to find the number GPON devices that is using in wide that show more than one million routers are actively working around the world.