Description
A newly disclosed vulnerability in WinRAR, tracked as CVE-2025-31334, allows attackers to bypass Windows’ Mark of the Web (MotW) security mechanism. This flaw affects all WinRAR versions prior to 7.11 and could allow malicious actors to execute arbitrary code on targeted systems without triggering typical Windows security alerts. The issue revolves around how WinRAR handles symbolic links (symlinks) when extracting and launching executable files. MotW is a security feature that tags files downloaded from the internet with metadata (zone-identifier) indicating potential risk. Windows then uses this data to prompt users before executing the file. This vulnerability effectively disables that protection in specific scenarios.
Attack Details
CVE-2025-31334 involves the use of specially crafted symbolic links inside WinRAR archives. When such a symlink points to an executable and is launched via the WinRAR shell, the MotW metadata is ignored, resulting in no security warning prompt from Windows. This allows attackers to stealthily execute malicious payloads without user suspicion. Notably, symlinks can only be created on Windows systems with administrator privileges, which slightly reduces the risk surface. However, it is a viable vector in scenarios where the attacker has admin access or can trick users into running crafted archives. This vulnerability is particularly concerning given its similarity to previously exploited flaws, such as the 7-Zip double-archiving MotW bypass used to deploy Smokeloader malware. Nation-state threat actors have been known to leverage such weaknesses for stealthy malware delivery.
Remediation
To mitigate and prevent exploitation of this vulnerability, follow these steps:
The Guyana National CIRT recommends that users and administrators review this alert and apply it where necessary.
PDF Download: WinRAR Vulnerability CVE-2025-31334 MotW Security Bypass
References