CVE-2021-30713: Apple macOS Big Sur Privacy Bypass Flaw

CVE-2021-30713 Overview

CVE-2021-30713 is a permissions validation vulnerability in Apple's Transparency, Consent, and Control (TCC) framework that affects macOS Big Sur and Mac OS X systems. The vulnerability stems from insufficient validation in how macOS handles application permissions, allowing a malicious application to bypass Privacy preferences that are designed to protect sensitive user data and system resources.

This vulnerability is particularly significant because Apple has confirmed active exploitation in the wild, and it has been added to the CISA Known Exploited Vulnerabilities (KEV) catalog, indicating its use in real-world attacks against organizations.

Critical Impact

A malicious application can bypass macOS Privacy preferences to gain unauthorized access to protected resources such as the camera, microphone, screen recording, and sensitive file system locations without user consent. This vulnerability has been actively exploited in the wild.

Affected Products

• Apple macOS Big Sur (versions prior to 11.4)
• Apple Mac OS X 10.15.7 (Catalina) with various security updates
• Apple macOS systems running vulnerable TCC framework versions

Discovery Timeline

• 2021-09-08 - CVE-2021-30713 published to NVD
• 2025-10-23 - Last updated in NVD database

Technical Details for CVE-2021-30713

Vulnerability Analysis

CVE-2021-30713 exploits a fundamental weakness in macOS's TCC framework, which is responsible for enforcing Privacy preferences and controlling application access to sensitive resources. The TCC framework maintains a database of permissions that users have granted to applications, governing access to components like the camera, microphone, contacts, photos, and screen recording capabilities.

The vulnerability exists because the TCC validation mechanism fails to properly verify the legitimacy of permission requests under certain conditions. This allows a malicious application to construct requests that appear authorized, effectively bypassing the user consent mechanism that macOS relies upon to protect privacy-sensitive resources.

The local attack vector requires an attacker to first gain code execution on the target system, typically through social engineering, drive-by downloads, or exploitation of another vulnerability. Once executing locally, the malicious application can leverage this flaw to silently access protected resources without triggering the standard user authorization dialogs.

Root Cause

The root cause is classified as CWE-862 (Missing Authorization). The TCC framework failed to implement proper authorization checks in certain code paths, creating a gap in the permission validation logic. This architectural weakness allowed applications to circumvent the established trust model that macOS uses to protect user privacy.

The TCC subsystem (tccd daemon) is responsible for brokering access requests between applications and protected resources. The vulnerability allowed malicious applications to either inject permissions directly into the TCC database or exploit trust relationships with applications that already possessed elevated permissions.

Attack Vector

The attack requires local access and low privileges to execute. An attacker leveraging this vulnerability would typically:

1. Deploy a malicious application on the target macOS system through phishing, malicious downloads, or bundled software
2. The malicious application exploits the TCC validation weakness to bypass permission dialogs
3. Unauthorized access is gained to protected resources (camera, microphone, screen recording, files)
4. Sensitive data is exfiltrated without the user's knowledge or consent

The vulnerability has been observed being exploited by the XCSSET malware family, which specifically targets developers through infected Xcode projects. XCSSET uses this TCC bypass to enable screen capture functionality for espionage purposes.

Detection Methods for CVE-2021-30713

Indicators of Compromise

• Unexpected modifications to TCC database files located at ~/Library/Application Support/com.apple.TCC/TCC.db
• Applications granted sensitive permissions (camera, microphone, screen recording) without user interaction
• Presence of XCSSET malware artifacts or suspicious Xcode project modifications
• Unusual processes accessing the TCC database or tccd daemon
• Screen recording or camera access from applications that should not have such permissions

Detection Strategies

• Monitor for unauthorized read/write operations to TCC database files
• Implement endpoint detection for known XCSSET malware signatures and behaviors
• Alert on applications accessing protected resources without corresponding user authorization events
• Audit the TCC database for unexpected permission grants, particularly for screen capture and input monitoring

Monitoring Recommendations

• Deploy SentinelOne Singularity Platform for real-time behavioral analysis of macOS systems
• Enable audit logging for TCC-related events using macOS Unified Logging (log show --predicate 'subsystem == "com.apple.TCC"')
• Monitor for process injection attempts and AppleScript abuse commonly associated with TCC bypass attacks
• Establish baseline of legitimate application permissions and alert on deviations

How to Mitigate CVE-2021-30713

Immediate Actions Required

• Update all affected macOS systems to Big Sur 11.4 or later immediately
• For Mac OS X 10.15.7 (Catalina) systems, apply the latest security updates as referenced in Apple Security Article HT212805
• Review TCC database entries for unauthorized permission grants and remove suspicious entries
• Scan systems for XCSSET malware and other threats known to exploit this vulnerability
• Implement application allowlisting to prevent unauthorized applications from executing

Patch Information

Apple has addressed this vulnerability in macOS Big Sur 11.4 through improved validation of permission requests. The fix strengthens the TCC framework's authorization checks to prevent bypass techniques.

Detailed patch information is available through:

• Apple Security Update HT212529
• Apple Security Article HT212805

Organizations should prioritize patching as this vulnerability is listed in the CISA Known Exploited Vulnerabilities Catalog with mandatory remediation requirements for federal agencies.

Workarounds

• If immediate patching is not possible, restrict installation of new applications to those from verified sources only
• Review and audit TCC database permissions regularly using sqlite3 queries against the TCC database
• Enable System Integrity Protection (SIP) and ensure it has not been disabled
• Consider network segmentation for systems that cannot be immediately patched to limit lateral movement potential
• Deploy endpoint protection solutions capable of detecting TCC bypass attempts and XCSSET-related activity

# Check TCC database for suspicious entries (run as user)
sqlite3 ~/Library/Application\ Support/com.apple.TCC/TCC.db "SELECT client,service,allowed FROM access WHERE allowed=1;"

# Verify System Integrity Protection status
csrutil status

# Check for unauthorized screen recording permissions
sqlite3 ~/Library/Application\ Support/com.apple.TCC/TCC.db "SELECT client FROM access WHERE service='kTCCServiceScreenCapture' AND allowed=1;"

# Review recent TCC-related system logs
log show --predicate 'subsystem == "com.apple.TCC"' --last 24h