Pierluigi Paganini
April 10, 2025
Kaspersky researchers reported that an APT group, tracked as ToddyCat, has exploited a vulnerability in ESET software to stealthily execute malware, bypassing security.
The vulnerability, tracked as CVE-2024-11859, is a DLL Search Order Hijacking issue that potentially allow an attacker with administrator privileges to load a malicious dynamic-link library and execute its code.
The flaw in ESET software was exploited to deploy TCESB, a stealthy C++ tool that bypasses security and monitoring tools to execute payloads.
In early 2024, Kaspersky researchers found the previously unseen C++ tool while investigating the attacks of the ToddyCat APT.
“Previously unseen in ToddyCat attacks, it is designed to stealthily execute payloads in circumvention of protection and monitoring tools installed on the device.” reads the report published by Kaspersky.
“Static analysis of the DLL library showed that all functions exported by it import functions with the same names from the system file version.dll (Version Checking and File Installation Libraries). List of functions exported by TCESB List of functions exported by TCESB This indicates that the attackers use a DLL-proxying technique (Hijack Execution Flow, T1574) to run the malicious code. By means of this technique, a malicious DLL exports all functions of a legitimate one, but instead of implementing them, redirects calls to these functions to the original DLL. This way, an application that loads the malicious library will continue to work as normal, with the malicious code running in the context of this application in the background.”
Researchers discovered that ESET’s command-line scanner (ecls) insecurely loaded a malicious version.dll (TCESB), enabling stealthy payload execution. The flaw, tracked as CVE-2024-11859, was reported to ESET, who patched it in January 2025.
“Dynamic analysis showed that the scanner insecurely loads the system library version.dll, first checking for the file in the current directory, then searching for it in the system directories. This can result in a malicious DLL library being loaded, which constitutes a vulnerability.” states the report.
The TCESB malware uses the Bring Your Own Vulnerable Driver (BYOVD) technique to evade detection by installing a vulnerable Dell driver (CVE-2021-36276) via Device Manager. It waits for a specific payload file, decrypts it using AES-128 with a key embedded in the file, and executes it from memory. The tool logs its activity in detail and supports extensionless encrypted payloads like kesp and ecore.
“On systems with an affected ESET product installed, an attacker could plant a malicious dynamic-link library to a specific folder and execute its content by running ESET Command Line Scanner, which would load the planted library instead of the intended system library.” reads ESET’s advisory.
“This technique did not elevate the privileges, though—the attacker would have already needed to have administrator privileges to perform this attack.”
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