CVE-2020-27932: Apple iCloud RCE Vulnerability

CVE-2020-27932 Overview

CVE-2020-27932 is a type confusion vulnerability in Apple's XNU kernel that affects macOS, iOS, iPadOS, and watchOS operating systems. The vulnerability exists in the kernel's turnstile subsystem, where improper state handling allows a malicious application to execute arbitrary code with kernel privileges. This critical flaw enables complete system compromise through local code execution.

Critical Impact

This vulnerability is actively exploited in the wild and is listed in CISA's Known Exploited Vulnerabilities (KEV) catalog. Successful exploitation allows attackers to gain kernel-level privileges, enabling complete device takeover, data exfiltration, and persistent access.

Affected Products

• Apple macOS Big Sur (versions prior to 11.0.1)
• Apple macOS Catalina (versions prior to 10.15.7 Supplemental Update)
• Apple macOS High Sierra and Mojave (prior to Security Update 2020-006)
• Apple iOS (versions prior to 14.2 and 12.4.9)
• Apple iPadOS (versions prior to 14.2)
• Apple watchOS (versions prior to 7.1, 6.2.9, and 5.3.9)
• Apple iCloud for Windows
• Apple iTunes for Windows

Discovery Timeline

• 2020-12-08 - CVE-2020-27932 published to NVD
• 2025-10-27 - Last updated in NVD database

Technical Details for CVE-2020-27932

Vulnerability Analysis

CVE-2020-27932 is a type confusion vulnerability (CWE-843) residing in Apple's XNU kernel, specifically within the turnstiles mechanism used for thread synchronization and priority inheritance. Type confusion occurs when the kernel incorrectly interprets an object's type, allowing attackers to manipulate memory in unintended ways.

The vulnerability requires local access and user interaction to exploit, typically through a malicious application installed on the target device. Once triggered, the flaw allows the attacker to confuse the kernel about the type of an object being processed, leading to memory corruption that can be leveraged for arbitrary code execution with kernel privileges.

Root Cause

The root cause of this vulnerability lies in improper state handling within the XNU kernel's turnstile subsystem. Turnstiles are kernel primitives used to manage priority inheritance when threads block waiting for resources. The type confusion arises when the kernel fails to properly validate or track the type of objects being manipulated during turnstile operations.

When an attacker provides crafted input that triggers the type confusion, the kernel misinterprets the memory layout of the affected object. This allows the attacker to corrupt adjacent kernel memory, overwrite function pointers, or manipulate other sensitive kernel data structures, ultimately achieving arbitrary code execution in kernel context.

Attack Vector

The attack requires local access to the target system and user interaction (such as opening a malicious application). The exploitation flow involves:

1. A malicious application is installed and executed on the target Apple device
2. The application triggers the type confusion condition in the kernel's turnstile handling code
3. The kernel incorrectly interprets object types, leading to memory corruption
4. The attacker leverages this corruption to gain kernel-level code execution
5. With kernel privileges, the attacker can bypass security controls, access protected data, and maintain persistent access

Technical details about the XNU kernel turnstiles type confusion are available in the Packet Storm Security Advisory and the Full Disclosure Mailing List Post.

Detection Methods for CVE-2020-27932

Indicators of Compromise

• Unusual kernel panic or crash logs related to turnstile operations
• Unexpected processes running with elevated privileges
• Signs of kernel memory corruption in system diagnostics
• Applications attempting to access kernel memory regions
• Anomalous system call patterns related to thread synchronization

Detection Strategies

• Monitor for applications attempting unusual kernel interactions or system calls
• Implement endpoint detection and response (EDR) solutions capable of detecting kernel-level exploitation attempts
• Review system logs for kernel panics or crashes that may indicate exploitation attempts
• Use behavioral analysis to identify applications exhibiting suspicious privilege escalation patterns

Monitoring Recommendations

• Enable comprehensive logging on macOS devices to capture kernel-level events
• Deploy SentinelOne Singularity platform for real-time kernel-level threat detection
• Monitor for installation of unsigned or suspicious applications
• Implement application allowlisting to prevent execution of unauthorized code
• Regularly audit device security configurations and patch compliance

How to Mitigate CVE-2020-27932

Immediate Actions Required

• Update all affected Apple devices to the latest patched versions immediately
• Verify that macOS systems are running Big Sur 11.0.1, Catalina 10.15.7 Supplemental Update, or have Security Update 2020-006 applied
• Ensure iOS devices are updated to version 14.2 or 12.4.9 (for older devices)
• Update watchOS devices to version 7.1, 6.2.9, or 5.3.9 as applicable
• Remove any suspicious or unauthorized applications from affected devices

Patch Information

Apple has released security updates addressing this vulnerability across all affected platforms. Organizations should apply the following updates:

• macOS Big Sur 11.0.1 - Apple Support Article HT211931
• macOS Catalina 10.15.7 Supplemental Update - Apple Support Article HT211947
• Security Update 2020-006 for High Sierra and Mojave - Apple Support Article HT211946
• iOS 14.2 and iPadOS 14.2 - Apple Support Article HT211929
• iOS 12.4.9 - Apple Support Article HT211940
• watchOS 7.1 - Apple Support Article HT211928
• watchOS 6.2.9 - Apple Support Article HT211944
• watchOS 5.3.9 - Apple Support Article HT211945

For additional information, refer to the CISA Known Exploited Vulnerabilities Catalog entry.

Workarounds

• Restrict installation of applications to those from trusted sources only (Mac App Store, verified developers)
• Enable Gatekeeper and ensure System Integrity Protection (SIP) is active on macOS systems
• Implement Mobile Device Management (MDM) to control application installation on corporate devices
• Limit user account privileges to reduce the impact of potential exploitation
• Consider network segmentation to isolate unpatched devices until updates can be applied

# Verify macOS version and security updates
sw_vers
softwareupdate --history

# Check System Integrity Protection status
csrutil status

# Verify Gatekeeper is enabled
spctl --status

# List installed security updates
system_profiler SPInstallHistoryDataType | grep -A 5 "Security Update"