CVE-2016-4749 in iOS
Summary
by MITRE
Printing UIKit in Apple iOS before 10 mishandles environment variables, which allows local users to discover cleartext AirPrint preview content by reading a temporary file.
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Analysis
by VulDB Data Team • 09/16/2022
The vulnerability identified as CVE-2016-4749 represents a critical security flaw in Apple iOS versions prior to 10.0 where the printing subsystem fails to properly manage environment variables during the AirPrint preview generation process. This issue stems from improper handling of temporary file creation and cleanup mechanisms within the UIKit framework, which is responsible for the graphical user interface components in iOS applications. The flaw specifically affects the AirPrint functionality that allows users to print documents directly from iOS devices to compatible printers, creating a pathway for unauthorized information disclosure through the manipulation of environment variables that control temporary file creation.
The technical implementation of this vulnerability occurs when iOS applications generate AirPrint previews, which require the creation of temporary files containing document content to facilitate the printing process. During this operation, the system does not adequately sanitize or restrict the environment variables that influence temporary file paths and permissions, allowing local attackers to predict and access these temporary files before they are properly deleted or secured. This misconfiguration results in cleartext preview content being exposed through the temporary file system, where sensitive information such as document contents, formatting details, and potentially personal data may be readable by unauthorized local processes or users with appropriate privileges.
The operational impact of this vulnerability extends beyond simple information disclosure, as it creates a persistent security risk for iOS devices that rely on AirPrint functionality. Attackers can exploit this weakness to gain access to confidential documents, personal communications, or business-sensitive information that would normally be protected during the printing preview process. The vulnerability is particularly concerning because it operates at the system level within the UIKit framework, meaning that any application with local access to the device can potentially exploit this flaw without requiring additional privileges or complex attack vectors. This makes it a significant concern for enterprise environments where iOS devices handle sensitive corporate data and personal information.
Security mitigation strategies for CVE-2016-4749 should prioritize the immediate upgrade of affected iOS versions to 10.0 or later, where Apple has implemented proper environment variable sanitization and temporary file management. Organizations should also implement additional monitoring of temporary file systems for unauthorized access attempts and consider restricting local application privileges where possible. The vulnerability aligns with CWE-276, which addresses improper file permissions and inadequate access control, and can be categorized under ATT&CK technique T1005 for data from local system, as it enables unauthorized access to sensitive data through local file system manipulation. Network administrators should also consider implementing endpoint protection measures that monitor for suspicious temporary file access patterns and ensure that all iOS devices within the organization maintain current security patches to prevent exploitation of this and related vulnerabilities.