Multiple threat actors, both state-sponsored and financially motivated, are exploiting the CVE-2025-8088 high-severity vulnerability in WinRAR for initial access and to deliver various malicious payloads.
The security issue is a path traversal flaw that leverages Alternate Data Streams (ADS) to write malicious files to arbitrary locations. Attackers have exploited this in the past to plant malware in the Windows Startup folder, for persistence across reboots.
Researchers at cybersecurity company ESET discovered the vulnerability and reported in early August 2025 that the Russia-aligned group RomCom had been exploiting it in zero-day attacks.
In a report today, the Google Threat Intelligence Group (GTIG) says that exploitation started as early as July 18, 2025, and continues to this day from both state-backed espionage actors and lower-tier, financially motivated cybercriminals.
"The exploit chain often involves concealing the malicious file within the ADS of a decoy file inside the archive.
"While the user typically views a decoy document, such as a PDF, within the archive, there are also malicious ADS entries, some containing a hidden payload while others are dummy data," Google researchers explain.
When opened, WinRAR extracts the ADS payload using directory traversal, often dropping LNK, HTA, BAT, CMD, or script files that execute on user login.
Among the state-sponsored threat actors that Google researchers observed exploiting CVE-2025-8088 are:
UNC4895 (RomCom/CIGAR) delivering NESTPACKER (Snipbot) via spearphishing to Ukrainian military units.
APT44 (FROZENBARENTS) using malicious LNK files and Ukrainian-language decoys for follow-on downloads.
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