DescriptionMultiple D-Link DSL gateway devices contain a command injection vulnerability in the dnscfg.cgi endpoint due to improper sanitization of user-supplied DNS configuration parameters. An unauthenticated remote attacker can inject and execute arbitrary shell commands, resulting in remote code execution. The affected endpoint is also associated with unauthenticated DNS modification (“DNSChanger”) behavior documented by D-Link, which reported active exploitation campaigns targeting firmware variants of the DSL-2740R, DSL-2640B, DSL-2780B, and DSL-526B models from 2016 through 2019. Exploitation evidence was observed by the Shadowserver Foundation on 2025-11-27 (UTC). Affected devices were declared end-of-life/end-of-service in early 2020.