CVE-2021-47803: iFunbox Privilege Escalation Vulnerability

CVE-2021-47803 Overview

CVE-2021-47803 is an unquoted service path vulnerability in iFunbox 4.2 that affects the Apple Mobile Device Service component. This local privilege escalation flaw allows attackers with local access to execute arbitrary code with LocalSystem privileges by placing a malicious executable in the unquoted service path. When the vulnerable service restarts, Windows will execute the attacker's payload instead of the legitimate service binary, granting full system-level access.

Critical Impact

Local attackers can achieve LocalSystem privilege escalation through the unquoted Apple Mobile Device Service path in iFunbox 4.2, enabling complete system compromise.

Affected Products

• iFunbox version 4.2
• Apple Mobile Device Service (as bundled with iFunbox)

Discovery Timeline

• 2026-01-16 - CVE-2021-47803 published to NVD
• 2026-01-16 - Last updated in NVD database

Technical Details for CVE-2021-47803

Vulnerability Analysis

This vulnerability is classified under CWE-428 (Unquoted Search Path or Element), a well-known class of Windows privilege escalation vulnerabilities. The Apple Mobile Device Service installed by iFunbox 4.2 uses a service path that contains spaces but is not enclosed in quotation marks. When Windows attempts to start such a service, it follows a predictable search order to resolve the executable path, checking for executables at each space boundary in the path.

The local attack vector requires an attacker to have local access to the target system and the ability to write files to specific directories within the service path. Once a malicious executable is placed in the appropriate location, it will be executed with LocalSystem privileges the next time the service starts, whether due to a system reboot, manual restart, or service crash recovery.

Root Cause

The root cause of this vulnerability is improper configuration of the Windows service binary path during iFunbox installation. When the Apple Mobile Device Service is registered, the ImagePath registry value is set without enclosing the path in quotation marks. This occurs when the installation path contains spaces (e.g., C:\Program Files\...), which is the default installation location for most Windows applications.

Windows services require quoted paths when they contain spaces to prevent ambiguous executable resolution. Without quotes, the Service Control Manager (SCM) parses the path incrementally at each space, attempting to execute files like C:\Program.exe before reaching the intended binary.

Attack Vector

The attack requires local access to the vulnerable system with write permissions to directories in the service path. An attacker would:

1. Identify the unquoted service path for the Apple Mobile Device Service
2. Determine a writable location within the search path hierarchy
3. Place a malicious executable named to match one of the intermediate path components
4. Wait for or trigger a service restart

When the service restarts, Windows SCM executes the attacker's binary with LocalSystem privileges, providing complete system access. This attack is particularly effective in environments where the attacker has limited user privileges but can write to certain shared directories.

The vulnerability exploitation details are documented in the Exploit-DB #50040 entry.

Detection Methods for CVE-2021-47803

Indicators of Compromise

• Unexpected executable files in directories like C:\Program.exe or C:\Program Files\Common.exe
• Service execution anomalies where the Apple Mobile Device Service spawns unusual child processes
• Modification timestamps on system directories that should not normally change
• Windows Event Log entries showing service failures or unexpected service restarts

Detection Strategies

• Query Windows services for unquoted paths using PowerShell: Get-WmiObject Win32_Service | Where-Object { $_.PathName -notmatch '^"' -and $_.PathName -match ' ' }
• Monitor file system changes in root directories and common path locations for suspicious executables
• Implement application whitelisting to prevent unauthorized binaries from executing with elevated privileges
• Use SentinelOne's behavioral AI to detect privilege escalation attempts through service manipulation

Monitoring Recommendations

• Enable Windows Security Event Log auditing for service configuration changes (Event ID 4697)
• Monitor process creation events for services spawning unexpected child processes
• Alert on file creation events in directories commonly exploited by unquoted path attacks
• Regularly audit service configurations for unquoted paths as part of security hardening assessments

How to Mitigate CVE-2021-47803

Immediate Actions Required

• Audit all Windows services for unquoted paths and remediate immediately
• Restrict write permissions on directories within the service search path
• Consider uninstalling iFunbox 4.2 if not business-critical until a patched version is available
• Implement application control policies to prevent unauthorized executable execution

Patch Information

No official patch information is available from the vendor at this time. Users should check the iFunbox Home Page for any security updates. Additional details are available in the VulnCheck Advisory for iFunbox.

Workarounds

• Manually fix the unquoted service path by adding quotation marks to the ImagePath registry value
• Restrict NTFS permissions on directories within the service path to prevent unauthorized file creation
• Use Windows Security policies to prevent service binaries from executing from non-standard locations
• Monitor and alert on any modifications to the Apple Mobile Device Service configuration

# Manual registry fix to quote the service path (run as Administrator)
# First, identify the current path:
reg query "HKLM\SYSTEM\CurrentControlSet\Services\Apple Mobile Device Service" /v ImagePath

# Then update with quoted path (adjust path as needed):
reg add "HKLM\SYSTEM\CurrentControlSet\Services\Apple Mobile Device Service" /v ImagePath /t REG_EXPAND_SZ /d "\"C:\Program Files\Common Files\Apple\Mobile Device Support\AppleMobileDeviceService.exe\"" /f