A vulnerability in Netgear small office/home office (SOHO) devices can be exploited by an attacker on the local area network (LAN) to execute code remotely with root privileges, GRIMM security researchers warn.
Tracked as CVE-2021-34991 (CVSS score of 8.8), the vulnerability is described as a pre-authentication buffer overflow and was found to affect a device’s Universal Plug-and-Play (UPnP) daemon.
Netgear SOHO devices affected by the bug include routers, modems, and WiFi range extenders, and GRIMM’s researchers say they were able to devise an exploit capable of compromising even fully patched devices that are running the default configuration.
The issue was discovered in upnpd daemon functions related to the handling of “unauthenticated HTTP SUBSCRIBE and UNSUBSCRIBE requests from clients that wish to receive updates whenever the network’s UPnP configuration changes.”
While the issue is a traditional stack overflow, without modern mitigations to provide protections against it, exploitation is complicated by the fact that the buffer containing user input is converted to lowercase before the overflow, meaning that no gadgets containing bytes with capital letters can be used, and because “the copy which overflows the stack is a string copy,” GRIMM explains.
The security researchers have released proof-of-concept (PoC) code that exploits the vulnerability and also published a detailed technical analysis of the security error.
Netgear has announced the availability of patches that address the vulnerability in numerous device models, including extenders, routers, DSL modem routers, aircards, and cable modems, encouraging users to download and install the fixes as soon as possible.
“NETGEAR is developing and testing additional firmware fixes, which we will release as they become available,” the company also announced.
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