CVE-2024-40858: macOS Sequoia Auth Bypass Vulnerability

CVE-2024-40858 Overview

CVE-2024-40858 is a permissions vulnerability in macOS Sequoia that allows malicious applications to access the Contacts database without obtaining proper user consent. This improper access control flaw (CWE-284) stems from insufficient permission restrictions in macOS's privacy protection mechanisms, enabling unauthorized data exfiltration from one of the most sensitive user data stores on the system.

Critical Impact

Malicious applications can silently access and exfiltrate user contact information including names, phone numbers, email addresses, and other personal data without triggering permission prompts or user awareness.

Affected Products

• macOS Sequoia versions prior to 15.1

Discovery Timeline

• 2026-04-02 - CVE-2024-40858 published to NVD
• 2026-04-02 - Last updated in NVD database

Technical Details for CVE-2024-40858

Vulnerability Analysis

This vulnerability represents an improper access control weakness in macOS's Transparency, Consent, and Control (TCC) framework. The TCC framework is designed to protect sensitive user data including Contacts, Calendar, Photos, and other privacy-sensitive resources by requiring explicit user consent before applications can access them.

In vulnerable versions, a permissions issue allows applications to bypass these protective mechanisms and access the Contacts database directly. The local attack vector requires an attacker to first gain the ability to execute code on the target system, either through a malicious application installation or by exploiting another vulnerability.

The impact is significant: attackers can read highly sensitive personal information including full names, phone numbers, email addresses, physical addresses, birthdays, and relationship information—all without the user's knowledge or consent.

Root Cause

The root cause is classified as CWE-284 (Improper Access Control), indicating that the permission validation logic contained insufficient restrictions. The macOS privacy subsystem failed to properly enforce access control checks under certain conditions, allowing applications to interact with the Contacts framework without triggering the required consent dialogs.

This type of flaw typically occurs when permission checks are not applied consistently across all code paths that access protected resources, or when certain API calls inadvertently bypass the intended security boundaries.

Attack Vector

The attack requires local access and low-privilege code execution on the target macOS system. An attacker could exploit this vulnerability through several scenarios:

1. Malicious Application Distribution: Distributing a seemingly benign application through unofficial channels that secretly harvests contact data
2. Supply Chain Compromise: Injecting malicious code into legitimate applications during build or distribution
3. Post-Exploitation Data Collection: Using this vulnerability as part of a broader attack chain after gaining initial access to the system

The exploitation does not require any user interaction beyond the initial application execution. Once the malicious code runs, it can silently enumerate and exfiltrate the entire Contacts database without displaying permission prompts.

Detection Methods for CVE-2024-40858

Indicators of Compromise

• Unexpected database queries to ~/Library/Application Support/AddressBook/ directories by unauthorized processes
• Applications accessing Contacts-related frameworks without corresponding TCC permission entries in the TCC database
• Unusual network traffic patterns following Contacts access, potentially indicating data exfiltration
• Process activity logs showing applications interacting with com.apple.AddressBook services without proper entitlements

Detection Strategies

• Monitor TCC database (~/Library/Application Support/com.apple.TCC/TCC.db) for discrepancies between granted permissions and actual resource access
• Implement endpoint detection rules that flag processes accessing Contacts APIs without corresponding TCC authorization records
• Deploy behavioral analysis to detect applications that access sensitive data stores immediately after installation or execution
• Use file integrity monitoring on Contacts database locations to track unauthorized read operations

Monitoring Recommendations

• Enable unified logging for privacy-related subsystems and regularly audit access to protected resources
• Implement application allowlisting to prevent unauthorized applications from executing
• Monitor for applications installed outside the Mac App Store that request or access sensitive data
• Review system logs for TCC-related errors or anomalies that may indicate bypass attempts

How to Mitigate CVE-2024-40858

Immediate Actions Required

• Update macOS Sequoia to version 15.1 or later immediately
• Audit installed applications and remove any untrusted or unnecessary software
• Review System Settings > Privacy & Security > Contacts to verify only trusted applications have access
• Consider restricting user ability to install applications from outside the Mac App Store

Patch Information

Apple has addressed this vulnerability in macOS Sequoia 15.1 by implementing additional permission restrictions. The fix strengthens the access control validation for Contacts data, ensuring all applications must properly request and receive user consent before accessing this sensitive information.

For detailed patch information and update instructions, refer to the Apple Support Document.

To update macOS:

1. Open System Settings
2. Navigate to General > Software Update
3. Install macOS Sequoia 15.1 or later

Workarounds

• Restrict application installation to Mac App Store only via MDM policies or parental controls
• Use application firewall rules to block network access for untrusted applications, limiting data exfiltration capability
• Implement endpoint protection solutions that can detect and block unauthorized data access attempts
• Regularly back up and audit Contacts data to detect potential unauthorized access or modifications

# Verify macOS version to confirm patch status
sw_vers -productVersion

# Check TCC database for Contacts permissions (requires Full Disk Access)
sqlite3 ~/Library/Application\ Support/com.apple.TCC/TCC.db "SELECT client, auth_value FROM access WHERE service='kTCCServiceAddressBook';"

# List applications with Contacts entitlements
find /Applications -name "*.app" -exec codesign -d --entitlements :- {} \; 2>/dev/null | grep -l "com.apple.developer.contacts"