CVE-2023-42940: Apple macOS Information Disclosure Flaw

CVE-2023-42940 Overview

CVE-2023-42940 is an information disclosure vulnerability in Apple macOS caused by a session rendering issue. The flaw exists in how macOS handles screen sharing sessions, where improper session tracking can lead to unintended content being shared with remote participants. This vulnerability was addressed by Apple with improved session tracking mechanisms in macOS Sonoma 14.2.1.

Critical Impact

Users sharing their screen may unintentionally expose sensitive content to remote participants, potentially leading to unauthorized disclosure of confidential information, credentials, or private data.

Affected Products

• Apple macOS (versions prior to macOS Sonoma 14.2.1)
• macOS Sonoma users utilizing screen sharing functionality

Discovery Timeline

• 2023-12-19 - CVE-2023-42940 published to NVD
• 2025-11-04 - Last updated in NVD database

Technical Details for CVE-2023-42940

Vulnerability Analysis

This vulnerability stems from a session rendering flaw in macOS's screen sharing functionality. When users initiate screen sharing sessions, the operating system's session tracking mechanism fails to properly correlate the intended display content with what is actually rendered and transmitted to remote viewers. This desynchronization between the user's intended shared content and the actual rendered output creates a scenario where unintended windows, applications, or screen regions may be inadvertently exposed to remote participants.

The vulnerability is classified under CWE-200 (Exposure of Sensitive Information to an Unauthorized Actor), highlighting its nature as an information disclosure issue. The attack requires network access and some user interaction, as the victim must actively initiate a screen sharing session.

Root Cause

The root cause of CVE-2023-42940 lies in improper session tracking within macOS's screen sharing subsystem. The rendering pipeline failed to maintain accurate synchronization between the user-selected content for sharing and the actual display buffer being transmitted. This session state management flaw allowed the wrong content to be captured and shared, bypassing the user's explicit selection of what to share.

Attack Vector

The vulnerability is exploitable over a network when a victim initiates a screen sharing session. An attacker positioned as a remote participant in the screen sharing session could passively observe content that the user did not intend to share. The exploitation requires:

1. The victim to initiate a screen sharing session (user interaction required)
2. The attacker to have access as a legitimate participant in the session
3. The session rendering bug to trigger, exposing unintended content

This is a passive information disclosure vulnerability where the attacker observes leaked content rather than actively injecting malicious payloads. The victim may remain unaware that incorrect content is being shared, as their local view may differ from what remote participants observe.

Detection Methods for CVE-2023-42940

Indicators of Compromise

• Unexpected screen content visible to remote participants during screen sharing sessions
• User reports of displayed content not matching intended shared content
• Anomalous session state behavior during screen sharing activities
• Discrepancies between local screen share preview and actual transmitted content

Detection Strategies

• Monitor for macOS versions prior to 14.2.1 in enterprise environments using endpoint management tools
• Implement endpoint detection rules to identify vulnerable macOS installations
• Review screen sharing session logs for anomalous behavior patterns
• Deploy SentinelOne agents configured to detect unpatched macOS systems

Monitoring Recommendations

• Enable enhanced logging for screen sharing activities on macOS endpoints
• Monitor network traffic during screen sharing sessions for unexpected data patterns
• Implement alerts for screen sharing sessions from systems running vulnerable macOS versions
• Conduct periodic vulnerability assessments to identify unpatched systems

How to Mitigate CVE-2023-42940

Immediate Actions Required

• Update all affected macOS systems to macOS Sonoma 14.2.1 or later immediately
• Audit enterprise environments to identify systems running vulnerable macOS versions
• Temporarily restrict or disable screen sharing functionality on unpatched systems
• Notify users about the potential for unintended content disclosure during screen sharing

Patch Information

Apple has released macOS Sonoma 14.2.1 which addresses this vulnerability with improved session tracking. The patch is available through standard macOS update mechanisms. System administrators should prioritize deployment of this update across all managed macOS endpoints.

For detailed patch information, refer to the Apple Support Document and the Apple Knowledge Base Article.

Workarounds

• Disable screen sharing functionality until patches can be applied
• Use alternative screen sharing solutions that do not rely on the affected macOS subsystem
• Implement strict access controls limiting who can participate in screen sharing sessions
• Close all sensitive applications and windows before initiating screen sharing sessions as a precautionary measure

# Check current macOS version
sw_vers -productVersion

# Disable screen sharing service temporarily (requires admin privileges)
sudo launchctl disable system/com.apple.screensharing

# Verify screen sharing is disabled
sudo launchctl print system/com.apple.screensharing