Endpoint Security
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Internet of Things Security
Botnet Operators Execute First Known Exploit of Nearly Decade-Old Flaw
Operators behind a botnet picked up on a nearly decade-old flaw in Asus routers allowing an unauthenticated attacker to achieve remote code execution as a root user.
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Researchers at VulnCheck flagged in-the-wild exploitation of CVE-2018-5999, a critical flaw carrying a 9.8 CVSS score, to the RondoDox botnet. The botnet, which surfaced in mid-2025 and focuses on Linux systems, is often classed as a variant of the Mirai botnet. “Unlike Mirai, this malware’s sole purpose is to execute DoS attacks, while Mirai is not only capable of doing DoS attacks but also scan and exploit other systems,” wrote Bitsight in March.
VulnCheck began observing exploitation of the Asus vulnerability on May 17. “Public exploits have been available since 2018,” wrote VulnCheck CTO Jacob Baines in a Friday LinkedIn post. “But until now, we hadn’t seen the vulnerability exploited in the wild.”
RondoDox relies on a multi-stage attack chain built around mass exploitation, particularly focusing on end-of-life and IoT devices. Its scans for exposed devices, attempting to exploit one of possibly dozens of embedded CVEs at once, often chaining flaws together before introducing a malware payload, which connects to command-and-control infrastructure.
“RondoDox is well known for implementing a ton of exploits. Some analyses have tracked its CVE associations well into the 170s, so it’s not surprising or new that they’re using older ones too,” said Baines.
According to Bitsight analysis, threat actors behind RondoDox likely monitor vulnerability disclosures, exploiting certain CVEs linked to consumer tech before publication. With “compromised residential IPs” serving as its hosting infrastructure, the botnet relies on older vulnerabilities found in “widely deployed, largely end-of-life consumer routers” to maintain persistence.
“There are a ton of Asus routers online, more than 1 million, so it’s very conceivable that this is working for RondoDox,” said Baines.