CVE-2026-28893: Apple macOS Information Disclosure Flaw

CVE-2026-28893 Overview

A privacy vulnerability exists in Apple macOS related to improper handling of temporary files during print preview operations. When a user initiates print preview functionality, the system may inadvertently write document contents to temporary files in an insecure manner, potentially exposing sensitive information to other local users or processes with access to the temporary file storage locations.

Critical Impact

Documents containing sensitive information may be written to temporary files during print preview, potentially exposing private data to unauthorized local access.

Affected Products

• Apple macOS (versions prior to macOS Tahoe 26.4)

Discovery Timeline

• 2026-03-25 - CVE CVE-2026-28893 published to NVD
• 2026-03-25 - Last updated in NVD database

Technical Details for CVE-2026-28893

Vulnerability Analysis

This vulnerability stems from improper temporary file handling within the macOS print preview subsystem. When users invoke print preview for documents, the operating system creates temporary files to render and display the document content. The vulnerability arises from insufficient protection mechanisms applied to these temporary files, allowing potential unauthorized access to document contents.

The local attack vector requires an attacker to have existing access to the target system. Once positioned on the system, an attacker could potentially monitor or access the temporary file storage locations used by the print preview functionality to extract sensitive document data. The integrity impact allows modification of data without proper authorization, though confidentiality and availability remain unaffected according to the vulnerability assessment.

Root Cause

The root cause of this vulnerability is improper handling of temporary files during the print preview process. The macOS print subsystem fails to implement adequate security controls when creating and managing temporary files, such as:

• Insufficient file permission restrictions on temporary files
• Inadequate cleanup of temporary files after print preview operations
• Potential use of predictable temporary file locations or naming conventions

These deficiencies enable local attackers with system access to potentially intercept or access document contents written to these temporary locations.

Attack Vector

The attack requires local access to the vulnerable macOS system. An attacker with low privileges on the target system could exploit this vulnerability by monitoring temporary file directories used by the print preview subsystem. When a legitimate user initiates print preview for a document containing sensitive information, the attacker could access the temporary file to view the document contents.

The exploitation scenario involves:

1. Attacker gains local access to a macOS system
2. Attacker monitors temporary file storage locations
3. A legitimate user opens a document and uses print preview
4. The system writes document content to a temporary file with insufficient protections
5. Attacker accesses the temporary file to obtain document contents

This vulnerability does not involve any remote exploitation capability and requires pre-existing local system access.

Detection Methods for CVE-2026-28893

Indicators of Compromise

• Unusual access patterns to system temporary directories such as /tmp or /var/folders
• Unexpected processes monitoring or reading files from temporary storage locations
• Evidence of file access timestamps on temporary files by non-printing processes

Detection Strategies

• Monitor file system access to temporary directories for anomalous read operations
• Implement endpoint detection rules to identify processes accessing temporary files created by print-related services
• Review audit logs for unauthorized access attempts to the print preview temporary file locations

Monitoring Recommendations

• Enable file system auditing for temporary directory access on macOS systems
• Deploy endpoint security solutions capable of monitoring file operations in real-time
• Implement behavioral analytics to detect unusual access patterns to temporary storage

How to Mitigate CVE-2026-28893

Immediate Actions Required

• Update macOS to version Tahoe 26.4 or later to apply Apple's security patch
• Restrict local user access on shared macOS systems to reduce attack surface
• Review and harden file permissions on temporary directories where feasible
• Avoid using print preview for highly sensitive documents until patch is applied

Patch Information

Apple has addressed this vulnerability in macOS Tahoe 26.4 with improved handling of temporary files. The fix ensures proper security controls are applied to temporary files created during print preview operations. Administrators should apply this update immediately on all affected macOS systems.

For detailed patch information and download instructions, refer to the Apple Support Article.

Workarounds

• Limit print preview usage for documents containing sensitive information until systems are patched
• Restrict local user access on macOS systems to minimize exposure to local privilege attacks
• Consider using alternative document viewing methods that do not invoke the print preview subsystem
• Implement strict access controls on shared macOS workstations

# Check current macOS version
sw_vers

# Verify system is updated to macOS Tahoe 26.4 or later
softwareupdate --list

# Apply available security updates
softwareupdate --install --all