A recently disclosed security flaw in OSGeo GeoServer GeoTools has been exploited as part of multiple campaigns to deliver cryptocurrency miners, botnet malware such as Condi and JenX, and a known backdoor called SideWalk.

The security vulnerability is a critical remote code execution bug (CVE-2024-36401, CVSS score: 9.8) that could allow malicious actors to take over susceptible instances.

In mid-July, the U.S. Cybersecurity and Infrastructure Security Agency (CISA) added it to its Known Exploited Vulnerabilities (KEV) catalog, based on evidence of active exploitation. The Shadowserver Foundation said it detected exploitation attempts against its honeypot sensors starting July 9, 2024.

According to Fortinet FortiGuard Labs, the flaw has been observed being used to deliver GOREVERSE, a reverse proxy server designed to establish a connection with a command-and-control (C2) server for post-exploitation activity.

These attacks are said to target IT service providers in India, technology companies in the U.S., government entities in Belgium, and telecommunications companies in Thailand and Brazil.

The GeoServer server has also served as a conduit for Condi and a Mirai botnet variant dubbed JenX, and at least four types of cryptocurrency miners, one of which is retrieved from a fake website that impersonates the Institute of Chartered Accountants of India (ICAI).

Perhaps the most notable of the attack chains leveraging the flaw is the one that propagates an advanced Linux backdoor called SideWalk, which is attributed to a Chinese threat actor tracked as APT41.

The starting point is a shell script that's responsible for downloading the ELF binaries for ARM, MIPS, and X86 architectures, which, in turn, extracts the C2 server from an encrypted configuration, connects to it, and receives further commands for execution on the compromised device.

This includes running a legitimate tool known as Fast Reverse Proxy (FRP) to evade detection by creating an encrypted tunnel from the host to the attacker-controlled server, allowing for persistent remote access, data exfiltration, and payload deployment.

"The primary targets appear to be distributed across three main regions: South America, Europe, and Asia," security researchers Cara Lin and Vincent Li said.

"This geographical spread suggests a sophisticated and far-reaching attack campaign, potentially exploiting vulnerabilities common to these diverse markets or targeting specific industries prevalent in these areas."

The development comes as CISA this week added to its KEV catalog two flaws found in 2021 in DrayTek VigorConnect (CVE-2021-20123 and CVE-2021-20124, CVSS scores: 7.5) that could be exploited to download arbitrary files from the underlying operating system with root privileges.