CVE-2024-38084: Microsoft OfficePlus Privilege Escalation

CVE-2024-38084 Overview

CVE-2024-38084 is an elevation of privilege vulnerability affecting Microsoft OfficePlus. This security flaw allows an attacker with local access and low-level privileges to elevate their permissions on affected systems, potentially gaining complete control over confidentiality, integrity, and availability of the compromised host.

Critical Impact

Successful exploitation enables local attackers to escalate privileges from a low-privileged user account to gain elevated access, potentially compromising the entire system through unauthorized file manipulation via symbolic link attacks.

Affected Products

• Microsoft OfficePlus (all versions prior to the security patch)

Discovery Timeline

• August 13, 2024 - CVE-2024-38084 published to NVD
• August 16, 2024 - Last updated in NVD database

Technical Details for CVE-2024-38084

Vulnerability Analysis

This vulnerability stems from improper link resolution before file access (CWE-59), commonly known as a symlink attack or link following vulnerability. The flaw exists in how Microsoft OfficePlus handles file operations, failing to properly validate the target of symbolic links before performing privileged operations. This oversight allows an attacker to redirect file operations to arbitrary locations on the file system.

The local attack vector requires the attacker to already have access to the target system with low-level user privileges. No user interaction is required for exploitation, making it suitable for automated attack chains once initial access is obtained.

Root Cause

The root cause of CVE-2024-38084 lies in the application's failure to properly resolve and validate symbolic links before performing file operations. When OfficePlus performs privileged file operations, it does not adequately verify whether the target path contains symbolic links pointing to sensitive system locations. This allows an attacker to create a symbolic link that redirects the application's file operations to protected files or directories, effectively leveraging the application's elevated privileges.

Attack Vector

An attacker with local access to the system can exploit this vulnerability by creating malicious symbolic links in directories where OfficePlus performs file operations. The attack flow typically involves:

1. Identifying file operations performed by OfficePlus with elevated privileges
2. Creating a symbolic link in the target directory pointing to a sensitive system file
3. Triggering the vulnerable file operation in OfficePlus
4. The application follows the symbolic link and performs the operation on the attacker-controlled target

This technique allows the attacker to overwrite, delete, or modify files they would not normally have access to, effectively escalating their privileges on the system.

Detection Methods for CVE-2024-38084

Indicators of Compromise

• Unusual symbolic link creation in OfficePlus installation or temporary directories
• Unexpected file modifications in Windows system directories following OfficePlus operations
• Anomalous privilege escalation events associated with OfficePlus processes
• Creation of junction points or symbolic links by low-privileged users targeting system paths

Detection Strategies

• Monitor for symbolic link creation events in directories used by Microsoft OfficePlus
• Implement file integrity monitoring on sensitive system files and directories
• Deploy endpoint detection rules that alert on symlink attacks targeting privileged applications
• Use Windows auditing to track file system redirection attempts

Monitoring Recommendations

• Enable Windows Security Event logging for file system operations (Event IDs 4663, 4656)
• Configure SentinelOne to detect privilege escalation attempts via symbolic link manipulation
• Monitor OfficePlus process behavior for unexpected file system access patterns
• Implement alerts for changes to system files following OfficePlus operations

How to Mitigate CVE-2024-38084

Immediate Actions Required

• Apply the latest security updates from Microsoft for OfficePlus immediately
• Review systems for evidence of exploitation or suspicious symbolic links
• Restrict user permissions to create symbolic links where possible using Group Policy
• Implement application whitelisting to prevent unauthorized executables from running

Patch Information

Microsoft has released a security update addressing this vulnerability. Administrators should apply the patch available through the Microsoft Security Response Center advisory. The update corrects how OfficePlus validates file paths before performing privileged operations, properly resolving symbolic links to prevent unauthorized file access.

Workarounds

• Restrict symbolic link creation using Windows Group Policy (SeCreateSymbolicLinkPrivilege)
• Limit local access to systems running OfficePlus to trusted users only
• Use Windows Defender Exploit Guard's Attack Surface Reduction rules to block exploitation techniques
• Monitor and restrict access to directories used by OfficePlus for temporary files

# Restrict symbolic link creation via Group Policy (PowerShell)
# Review current user rights assignment for symbolic link creation
secedit /export /cfg c:\secpol.cfg
# Remove untrusted users from SeCreateSymbolicLinkPrivilege