CVE-2024-23745: Notion Web Clipper RCE Vulnerability

CVE-2024-23745 Overview

CVE-2024-23745 is a command injection vulnerability affecting Notion Web Clipper version 1.0.3(7) on macOS. The vulnerability stems from the application's .nib files being susceptible to the "Dirty NIB" attack technique, which allows attackers to manipulate NIB files to execute arbitrary commands within the application's context. This is particularly concerning because macOS Gatekeeper may still permit execution of the application even after NIB file modification, bypassing intended security controls.

Critical Impact

Attackers can achieve arbitrary command execution by manipulating NIB files within the Notion Web Clipper application, potentially leading to full system compromise while bypassing macOS Gatekeeper protections.

Affected Products

• Notion Web Clipper 1.0.3(7)

Discovery Timeline

• 2024-01-31 - CVE-2024-23745 published to NVD
• 2024-11-21 - Last updated in NVD database

Technical Details for CVE-2024-23745

Vulnerability Analysis

This vulnerability leverages the Dirty NIB attack technique, which exploits how macOS applications handle NIB (NeXT Interface Builder) files. NIB files are serialized user interface objects used by macOS applications to define their graphical interfaces. When these files are loaded, they can instantiate objects and call methods, which creates an opportunity for code execution.

The core issue lies in how Notion Web Clipper loads and trusts NIB files within its application bundle. An attacker with the ability to modify these NIB files can inject malicious object configurations that execute arbitrary commands when the application loads the compromised interface elements. The vulnerability is classified as CWE-77 (Command Injection).

Notably, the vendor has indicated that this vulnerability is related to CVE-2022-48505 and represents a macOS-level caching issue rather than a product-specific flaw. The vendor's position is that Gatekeeper's incorrect caching of file signatures enables this attack vector, making it difficult to address at the application level.

Root Cause

The root cause involves two interrelated issues:

1. NIB File Trust Model: The application loads and executes serialized objects from NIB files without adequate validation of their integrity or origin after initial verification.

2. Gatekeeper Caching Flaw: macOS Gatekeeper caches the signature verification of applications, allowing modified NIB files to be executed even after tampering because the application's overall signature was previously validated.

This creates a scenario where an attacker who gains write access to the application bundle can inject malicious code that executes with the application's privileges and entitlements.

Attack Vector

The attack requires local access to modify the NIB files within the Notion Web Clipper application bundle. The attack flow involves:

1. An attacker locates the target .nib file within the Notion Web Clipper application bundle
2. The attacker modifies the NIB file to include malicious object instantiations that execute arbitrary commands
3. When the user launches Notion Web Clipper, the tampered NIB file is loaded
4. Due to Gatekeeper's signature caching behavior, the application executes normally despite the modification
5. The malicious payload executes within the application's security context

The Dirty NIB technique leverages Cocoa's object serialization capabilities, where NIB files can contain object references that trigger method calls during deserialization. Attackers craft NIB files that instantiate objects configured to execute shell commands or load malicious code.

For detailed technical information about the Dirty NIB attack technique, refer to the XPN Security Blog Post which provides in-depth analysis of the exploitation methodology. The GitHub CVE-2024-23745 Repository contains additional technical details specific to this vulnerability.

Detection Methods for CVE-2024-23745

Indicators of Compromise

• Unexpected modifications to .nib files within the Notion Web Clipper application bundle
• Changes to file hashes of NIB resources in /Applications/Notion Web Clipper.app/Contents/Resources/
• Unusual child processes spawned by Notion Web Clipper
• Suspicious command-line activity originating from the Web Clipper application context

Detection Strategies

• Monitor file integrity of application bundles, specifically tracking modifications to .nib files after initial installation
• Implement endpoint detection rules to alert on unexpected process spawning from browser extension helper applications
• Use code signing validation tools to verify application bundle integrity before execution
• Deploy behavioral analysis to detect command execution patterns inconsistent with normal Notion Web Clipper operations

Monitoring Recommendations

• Configure file integrity monitoring (FIM) for critical application directories, particularly the Notion Web Clipper application bundle
• Enable detailed process creation logging on macOS endpoints to capture parent-child process relationships
• Review system logs for Gatekeeper warnings or signature verification anomalies
• Implement application allowlisting that validates entire application bundles rather than just executables

How to Mitigate CVE-2024-23745

Immediate Actions Required

• Verify the integrity of the Notion Web Clipper application bundle using code signing verification tools
• Consider removing or disabling Notion Web Clipper until a patched version addressing this issue is available
• Implement strict file system permissions to prevent unauthorized modification of application bundles
• Enable SIP (System Integrity Protection) and ensure it remains active to protect critical system areas

Patch Information

The vendor has stated that this vulnerability is related to the underlying macOS Gatekeeper caching behavior (CVE-2022-48505) and cannot be effectively addressed at the product level. Users should monitor for macOS updates from Apple that address the signature caching issue. Additionally, keep Notion Web Clipper updated to the latest version as the vendor may implement additional mitigations in future releases.

Workarounds

• Restrict write access to the /Applications directory to prevent unauthorized modification of application bundles
• Use application firewall rules to limit network access for Notion Web Clipper to reduce potential impact of compromise
• Consider using the Notion web interface directly instead of the browser extension in high-security environments
• Implement endpoint protection solutions capable of detecting Dirty NIB attack patterns and command injection attempts
• Regularly verify application bundle integrity using codesign -vvv --deep commands

# Verify Notion Web Clipper application signature integrity
codesign -vvv --deep "/Applications/Notion Web Clipper.app"

# Check for unauthorized modifications to NIB files
find "/Applications/Notion Web Clipper.app" -name "*.nib" -exec shasum -a 256 {} \;

# Monitor for unexpected child processes from the application
ps aux | grep -i "Notion Web Clipper"