DD-WRT is a popular open-source firmware used in many wireless routers, which are commonly used to manage network access for websites and other online services you may host. A stack-based buffer overflow vulnerability has been found in this firmware. This flaw affects an internal buffer used by DD-WRT’s UPnP feature, a tool that lets devices on your local network automatically connect to each other without manual configuration. A buffer overflow is a type of coding error that occurs when a program writes more data to a temporary memory section than that section can hold. An attacker does not need any login credentials or prior access to your network to exploit this vulnerability. They could trigger the overflow to run unauthorized code on your router, which may disrupt your website or other online services, or allow the attacker to access data passing through your network.
Source: CISA Known Exploited Vulnerabilities Catalog — https://nvd.nist.gov/vuln/detail/CVE-2021-27137
