HOW A RUSSIAN THREAT ACTOR USES A RECENT WINRAR VULNERABILITY IN THEIR UKRAINE OPERATIONS

Summary from the TLDR InfoSec newsletter

Primitive Bear (Gamaredon), an FSB-attributed APT group, exploited CVE-2025-6218, a critical WinRAR path traversal vulnerability affecting versions through 7.11, in targeted spear-phishing campaigns against Ukrainian military units and government entities using military-themed lures. The attack chain leveraged malicious RAR archives containing HTA files with obfuscated VBScript, weaponizing a path traversal flaw to write payloads directly to Windows Startup folders, then used mshta.exe as a LOLBIN to fetch secondary-stage malware from a DynDNS-based C2 infrastructure across 14 active domains. The campaigns demonstrated sophisticated tradecraft, including minimal obfuscation, multi-stage payload delivery, phishing URL masquerading (president.gov.ua@malicious-domain), and infrastructure leveraging InterLIR IP marketplaces and No-IP dynamic DNS services. Defenders are recommended to update WinRAR to 7.12+, block HTA execution via AppLocker/WDAC, and monitor LOLBIN abuse and Startup folder modifications.