Google Threat Intelligence Group analyzed STOCKSTAY, a modular .NET backdoor developed and operated by Turla since late 2022, which uses a WebSocket-based C2 channel, RSA/AES encrypted communications, and IPC via WM_COPYDATA between its downloader, orchestrator, tunneler, and backdoor components. STOCKSTAY exhibits strong code, architectural, and obfuscation (K1MORPHER) overlaps with KAZUAR, suggesting a shared development team, and has been deployed via phishing (malicious RDP files, HTA lures) and, most recently, exploitation of CVE-2025-8088 in WinRAR to target Ukrainian military personnel. The actor leverages legitimate hosting platforms (Render, Glitch, GitHub) and compromised third-party/government infrastructure to obscure C2 infrastructure and complicate attribution.
CVE-2025-8088
3 posts
STOCKSTAY Another Day: The Latest Addition to Turla’s Intelligence Gathering Apparatus Gamaredon in 2025: Leveraging tunnels, workers, dead drops, and new alliances Gamaredon, a Russia-aligned APT group attributed to the FSB, maintained high operational tempo throughout 2025 with 35 spearphishing campaigns exclusively targeting Ukrainian government and military institutions. The group introduced six new PowerShell tools, resurrected the PteroSetup VBScript weaponizer for lateral movement, and began abusing CVE-2025-8088 (WinRAR) for persistence via the Startup folder. A significant infrastructure evolution occurred: C&C servers are now hidden behind tunnel services (Cloudflare tunnels, Cloudflare workers, Microsoft devtunnels, Loophole) and dead-drop resolutions on legitimate platforms (Telegram, Telegra.ph, Rentry, GoFile, Dropbox, and others), while stolen data is exfiltrated to S3-compatible cloud storage (Wasabi, Tebi, Intercolo) rather than attacker-owned servers.
Old WinRAR Flaw Fuels Attacks on Ukraine: How Unmanaged Software Keeps the Door Open Multiple Russia-aligned threat actors, including SHADOW-EARTH-066 and Earth Dahu, are actively exploiting a patched WinRAR path traversal vulnerability (CVE-2025-8088) to target Ukrainian organizations. The attackers use crafted RAR archives with NTFS Alternate Data Streams to silently drop malicious payloads, such as the evolved GIFTEDCROOK infostealer or HTA-based espionage tools, into the Windows Startup folder and ProgramData directories.
