Executive brief
7-Zip is a popular file compression and extraction utility. A vulnerability in how it handles certain archive files allows an attacker to bypass Windows security warnings (Mark-of-the-Web) and modify the contents of extracted files without the user's knowledge. This could lead to a user unknowingly running malicious files that they believe are safe or have been vetted by system security checks like SmartScreen.
Technical details
7-Zip for Windows (through version 26.02) contains a protection mechanism failure when extracting RAR5 archives containing Alternate Data Streams (ADS). The application attempts to suppress archive-supplied 'Zone.Identifier' streams to ensure the system's own Mark-of-the-Web (MotW) is propagated; however, it uses an exact string match. An attacker can use the NTFS-canonicalized name ':Zone.Identifier:$DATA' to bypass this check, overwriting the MotW with a 'ZoneId=0' (Trusted) marker. Additionally, using the '::$DATA' stream name allows an attacker to overwrite the primary file data. This combination enables the delivery of malicious payloads that bypass SmartScreen and other MotW-based security controls. Exploitation requires a user to extract a specially crafted RAR5 archive.
Affected products
- 7-Zip 7-Zip through 26.02
Timeline
- 2026-06-27: disclosed: Initial disclosure by VulnCheck
- 2026-06-28: advisory: NVD publication date