The Russian hacking group Gamaredon is actively leveraging a WinRAR vulnerability to distribute malware aimed at Ukrainian targets. This campaign, focused on data theft and system infiltration, utilizes a known flaw in WinRAR identified as CVE-2025-8088. The flaw enables the delivery of malicious payloads, including the GammaPhish HTML Application and subsequent downloads of VBScript malware.
Exploiting WinRAR for Cyber Attacks
According to cybersecurity firm Sekoia, the attack chain begins with the exploitation of the CVE-2025-8088 vulnerability in WinRAR. Once exploited, it launches the GammaPhish payload, which in turn downloads GammaLoad, a VBScript component. This infection sequence, first observed in January 2026, allows attackers to manipulate network configurations and execute arbitrary scripts on compromised systems.
The primary goal of Gamaredon appears to be gathering intelligence by fingerprinting host systems and executing malicious scripts. The use of dead drop resolvers (DDRs) helps in maintaining a stealthy presence, while the malware communicates with command-and-control (C2) servers to execute its payloads.
Malware Families: GammaWorm and GammaSteel
Among the deployed malware is GammaWorm, a VBScript-based worm that establishes persistence through scheduled tasks. It conceals itself by hiding legitimate directories and replacing them with malicious shortcut files on network shares and USB drives. This allows it to execute harmful code from C2 servers while staying undetected by blending in with normal traffic, particularly through platforms like Telegram.
GammaSteel, another malware variant delivered by GammaLoad, acts as an information stealer. It targets files with specific extensions and exfiltrates them to Amazon Web Services (AWS) S3 buckets or other attacker-controlled servers, depending on the situation. This dual approach of using legitimate services helps evade detection and maintain a long-term espionage operation.
Implications for Ukrainian Security
Gamaredon’s operations are part of a broader state-sponsored campaign linked to the Federal Security Service (FSB) of Russia. Their tactics have historically focused on Ukrainian government, military, and critical infrastructure, often using spear-phishing emails with malicious attachments. The current infection chain showcases a sophisticated and adaptable design that is likely to be repurposed in future attacks.
In addition to Gamaredon’s activities, other threat groups like UAC-0184 and UAC-0247 have also targeted Ukraine, using various techniques such as LNK lures and HTML Application droppers. These coordinated efforts highlight the ongoing cyber threat landscape faced by Ukraine, necessitating robust cybersecurity measures and constant vigilance.
As cyber threats continue to evolve, understanding the mechanisms and impacts of these attacks is crucial for developing effective defense strategies. The resilience and adaptability of the Gamaredon group’s tactics underscore the importance of staying informed and prepared for future challenges in cybersecurity.
