Exploited TP-Link Vulnerability Spawns Botnet Threats

Half a dozen different botnets are prowling the internet for TP-Link-brand Wi-Fi routers unpatched since last summer with the goal of commandeering them into joining distributed denial-of-service attacks.

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Chinese router manufacture TP-Link in June patched a command injection vulnerability in its Archer AX21 router, a residential model that retails for less than $100. Consumer-grade routers are notorious for uneven patching, either because manufacturers are slow to develop patches or consumers don’t apply them. “Once they’re connected to the internet, they don’t care anymore about the router,” one industry CISO told Oxford University academics researching a 2023 paper.

The vulnerability, tracked as CVE-2023-1389, allows attackers to insert malicious commands by calling the “locale” API on the web management interface. Attackers use set_country to insert remote code since the unpatched routers don’t sanitize that input.

Researchers at Fortinet said Tuesday they’ve observed multiple attacks over the past month focused on exploiting the vulnerability – including botnets Moobot, Miori, the Golang-based agent “AGoent,” a Gafgyt variant and an unnamed variant of the infamous Mirai botnet. Operators of the many Mirai-derived botnets have previously targeted the Archer AX21, Fortinet said in 2023 (see: Breach Roundup: Winter Vivern Hunting for Emails).

The AGoent bot deployed in these attacks exhibits intricate behaviors aimed at evading detection and establishing persistence. AGoent is capable of executing various malicious actions such as DDoS attacks, cryptocurrency mining and the installation of supplementary malware.

A variant of the Gafgyt bot, also known as Bashlite, uses the vulnerability to expand DDoS attacks on Linux-based systems. By downloading and executing malicious scripts, the Gafgyt variant establishes connections with command-and-control servers, awaiting instructions to launch coordinated attacks on targeted victims. The Mirai derivations, including Miori, use similar attack methodologies.

Another botnet looking for unpatched TP-Link is called Condi. Fortinet in 2023 reported a DDoS-for hire service selling website disruptions with Condi – which is also a Mirai variant. The botnet specifically targets consumer-grade Wi-Fi routers operating on unpatched firmware. DDoS-for-hire sites typically market themselves as “stressers” or “boosters” in a barely-there attempt to disguise their illegal nature.

A threat actor advertised the Condi botnet through a “Condi Network” Telegram channel launched in May 2022 and was monetizing the service by offering distributed denial-of-service attacks and selling the source code for the botnet itself (see: Surging Condi Botnet Campaign Hits Unpatched TP-Link Routers).

Researchers from Trend Micro’s Zero Day Initiative in April 2023 reported that CVE-2023-1389 had been “added to the Mirai botnet arsenal.” Devices in Eastern Europe appeared to fall victim first, but infections spread globally.