CVE-2024-8811: WinZip Mark-of-the-Web Bypass RCE Flaw

CVE-2024-8811 Overview

CVE-2024-8811 is a Mark-of-the-Web (MotW) bypass vulnerability affecting WinZip archive handling. This vulnerability allows remote attackers to bypass the Mark-of-the-Web protection mechanism on affected installations of WinZip. User interaction is required to exploit this vulnerability, as the target must visit a malicious page or open a malicious file.

The specific flaw exists within the handling of archive files. When opening an archive that bears the Mark-of-the-Web, WinZip removes the Mark-of-the-Web from the archive file. Following extraction, the extracted files also lack the Mark-of-the-Web. An attacker can leverage this vulnerability to execute arbitrary code in the context of the current user.

Critical Impact

Attackers can bypass Windows security protections and execute malicious code without triggering security warnings that normally protect users from untrusted files downloaded from the internet.

Affected Products

• WinZip (all versions prior to patched release)

Discovery Timeline

• 2024-11-22 - CVE-2024-8811 published to NVD
• 2025-01-03 - Last updated in NVD database

Technical Details for CVE-2024-8811

Vulnerability Analysis

The vulnerability stems from improper handling of the Mark-of-the-Web (MotW) alternate data stream attribute during archive extraction operations. The Mark-of-the-Web is a critical Windows security feature that identifies files downloaded from untrusted sources (internet, email attachments) by adding a Zone.Identifier alternate data stream (ADS) to files. This marker triggers additional security prompts and restrictions when users attempt to open or execute these files.

When WinZip processes an archive file that contains the MotW attribute, it improperly strips this security marker from the archive itself. More critically, when files are extracted from such an archive, the extracted files do not inherit or receive the Mark-of-the-Web designation. This behavior effectively "launders" potentially malicious files, removing the security context that Windows uses to protect users from untrusted content.

Root Cause

The root cause is classified under CWE-693 (Protection Mechanism Failure) and CWE-670 (Always-Incorrect Control Flow Implementation). WinZip fails to properly propagate the Mark-of-the-Web security attribute from source archives to extracted files. The application incorrectly handles the Zone.Identifier alternate data stream, removing it during the archive opening process rather than preserving and transferring this critical security metadata to all extracted contents.

Attack Vector

The attack vector requires local access with user interaction. An attacker must craft a malicious archive file containing harmful executables, scripts, or documents. The attack flow proceeds as follows:

1. The attacker creates a malicious archive containing harmful files (executables, Office documents with macros, scripts, etc.)
2. The archive is delivered to the victim via phishing email, malicious website, or other delivery mechanism
3. Upon download, Windows correctly marks the archive with the Mark-of-the-Web
4. The victim opens the archive with WinZip, which removes the MotW from the archive
5. When files are extracted, they lack the MotW security marker
6. The victim can now execute the malicious files without receiving Windows security warnings
7. Malicious code executes in the context of the current user

This bypass is particularly dangerous because it undermines a fundamental Windows security mechanism that users rely on to identify and protect themselves from untrusted files.

Detection Methods for CVE-2024-8811

Indicators of Compromise

• Executable files or scripts in user directories that lack expected Zone.Identifier alternate data streams despite being recently downloaded
• Archive extraction activity followed immediately by execution of previously unknown binaries
• Presence of malicious files that were delivered via archive formats commonly associated with WinZip (.zip, .zipx, .7z)

Detection Strategies

• Monitor for process execution events where the parent process is WinZip and child processes are executing from user-writable directories
• Implement endpoint detection rules that flag execution of files lacking MotW in download or temp directories
• Deploy behavioral analytics to detect archive extraction followed by immediate script or binary execution patterns

Monitoring Recommendations

• Enable detailed file system auditing to track alternate data stream operations on archive files
• Configure security tools to alert on execution of unsigned or untrusted binaries from common extraction paths
• Implement application control policies that restrict execution from user-writable directories regardless of MotW status

How to Mitigate CVE-2024-8811

Immediate Actions Required

• Update WinZip to the latest available version that addresses this vulnerability
• Consider using alternative archive utilities that properly preserve Mark-of-the-Web attributes until WinZip is patched
• Implement application whitelisting or execution policies to prevent unauthorized code execution regardless of MotW status
• Educate users about the risks of opening archives from untrusted sources

Patch Information

Users should consult the Zero Day Initiative Advisory ZDI-24-1234 for detailed patch information and vendor response. Update WinZip through the official WinZip website or application update mechanism to ensure the latest security fixes are applied.

Workarounds

• Extract archives in a sandboxed environment or virtual machine where MotW bypass has limited security impact
• Use alternative archive tools (such as 7-Zip or Windows built-in extraction) that properly handle Mark-of-the-Web propagation
• Implement group policies that restrict execution of files from common download and extraction directories
• Deploy endpoint protection solutions that do not solely rely on MotW for threat detection

# PowerShell: Check if a file has Mark-of-the-Web
# Use this to verify if extracted files retained their security marker
Get-Item -Path "C:\path\to\extracted\file.exe" -Stream Zone.Identifier -ErrorAction SilentlyContinue

# If no output, the file lacks MotW protection
# Consider implementing additional execution restrictions for such files