The remote code execution flaw, CVE-2021-35395, was seen in Mirai malware binaries by threat intel firm Radware, which “found that new malware binaries were published on both loaders leveraged in the campaign.”
Warning that the vuln had been included in Dark.IoT’s botnet “less than a week” after it was publicly disclosed, Radware said: “This vulnerability was recently disclosed by IoT Inspectors Research Lab on August 16th and impacts IoT devices manufactured by 65 vendors relying on the Realtek chipsets and SDK.”
The critical vuln, rated 9.8 on the CVSS scale, consists of multiple routes to cause buffer overflows (PDF from Realtek with details) in the web management interface provided by Realtek in its Jungle SDK for its router chipset. CVE-2021-35395 is a denial-of-service vuln; crafted inputs from an attacker can be used to crash the HTTP server running the management interface, and thus the router.
Rather than having the capability to develop its own exploits, Dark.IoT sits around waiting for white hats to publish proof-of-concepts for newly discovered vulns, and Smith said they incorporate those into their botnet within “days.”
While Realtek has patched the vulns in the SDK, vendors using its white-label tech now have to distribute patches for their branded devices and then users have to install them – all while Dark.IoT and other Mirai-based criminals are looking for exploitable devices.