CVE-2026-20699: Apple macOS Information Disclosure Flaw

CVE-2026-20699 Overview

A downgrade vulnerability affecting Intel-based Mac computers has been identified in Apple macOS. The flaw stems from insufficient code-signing restrictions that could allow a malicious application to bypass security controls and access user-sensitive data. Apple has addressed this issue by implementing additional code-signing restrictions across multiple macOS versions.

Critical Impact

A locally installed malicious application could exploit this downgrade vulnerability to bypass code-signing protections and gain unauthorized access to sensitive user data on Intel-based Mac systems.

Affected Products

• Apple macOS Sequoia versions prior to 15.7.5
• Apple macOS Sonoma versions prior to 14.8.5
• Apple macOS Tahoe versions prior to 26.3 and 26.4

Discovery Timeline

• March 25, 2026 - CVE-2026-20699 published to NVD
• March 25, 2026 - Last updated in NVD database

Technical Details for CVE-2026-20699

Vulnerability Analysis

This vulnerability is classified under CWE-347 (Improper Verification of Cryptographic Signature), indicating a fundamental weakness in how code-signing validation was implemented on Intel-based Mac computers. The flaw allows attackers to circumvent signature verification mechanisms that normally prevent unauthorized or modified code from executing with elevated trust levels.

The vulnerability requires local access to exploit, meaning an attacker would need to install a malicious application on the target system. Once executed, the malicious app can leverage the downgrade attack to bypass code-signing restrictions and access data that should be protected from unauthorized applications. The attack does not require any privileges or user interaction to succeed once the malicious application is present on the system.

The impact is primarily focused on confidentiality, as successful exploitation allows reading of user-sensitive data without the ability to modify system files or cause system disruption.

Root Cause

The root cause lies in improper verification of cryptographic signatures within the macOS code-signing framework on Intel-based systems. The vulnerability allowed applications to downgrade security checks or bypass signature validation requirements, enabling untrusted code to access protected resources. Apple resolved this by implementing additional code-signing restrictions that prevent these downgrade scenarios.

Attack Vector

The attack requires local access to the target Mac system with Intel architecture. An attacker must deliver and execute a malicious application on the victim's computer. This could be achieved through various methods including:

The malicious application exploits weaknesses in the code-signing verification process to present itself as trusted or to bypass signature checks entirely. Once the downgrade attack succeeds, the application gains access to user-sensitive data that would normally be protected from unauthorized access by the macOS security model.

Since no verified code examples are available for this vulnerability, the technical exploitation details can be found in Apple Support Document 126348 and related security advisories. The vulnerability mechanism involves manipulating code-signing verification to access protected data stores.

Detection Methods for CVE-2026-20699

Indicators of Compromise

• Unusual application behavior attempting to access protected user data directories
• Applications with suspicious or missing code signatures executing on Intel-based Macs
• Unexpected code-signing verification failures or bypass attempts in system logs
• Anomalous access patterns to sensitive user data by non-standard applications

Detection Strategies

• Monitor for applications attempting to access protected data stores without proper entitlements
• Implement endpoint detection rules to identify code-signing bypass attempts
• Review system integrity logs for signature verification anomalies on Intel-based Mac systems
• Use SentinelOne Singularity Platform to detect malicious applications attempting unauthorized data access

Monitoring Recommendations

• Enable verbose logging for code-signing events in macOS system logs
• Monitor application installation and execution events on Intel-based Mac endpoints
• Deploy behavioral detection to identify applications accessing user-sensitive data unexpectedly
• Establish baseline behaviors for legitimate applications to identify anomalous access patterns

How to Mitigate CVE-2026-20699

Immediate Actions Required

• Update all Intel-based Mac systems to the latest patched macOS versions immediately
• Review installed applications for unauthorized or suspicious software
• Implement application allowlisting to prevent unauthorized applications from executing
• Audit recent data access logs for signs of potential compromise

Patch Information

Apple has released security updates that address this vulnerability by implementing additional code-signing restrictions. Organizations should update to the following versions:

• macOS Sequoia - Update to version 15.7.5 or later
• macOS Sonoma - Update to version 14.8.5 or later
• macOS Tahoe - Update to version 26.3 or 26.4 or later

For detailed patch information, refer to the official Apple security advisories: Apple Support Document 126348, Apple Support Document 126794, Apple Support Document 126795, and Apple Support Document 126796.

Workarounds

• Restrict installation of applications to those from trusted sources and the Mac App Store only
• Implement strict application control policies using MDM solutions for managed Mac environments
• Enable Gatekeeper to maximum protection level to prevent unauthorized application execution
• Limit user privileges to reduce the impact of potential exploitation

# Enable Gatekeeper to App Store and identified developers only
sudo spctl --master-enable

# Verify Gatekeeper status
spctl --status

# Check system for unsigned or invalidly signed applications
find /Applications -name "*.app" -exec codesign -dv {} \; 2>&1 | grep -E "(not signed|invalid)"