CVE-2015-3797 in Mac OS X
Summary
by MITRE
The TRE library in Libc in Apple iOS before 8.4.1 and OS X before 10.10.5 allows context-dependent attackers to execute arbitrary code or cause a denial of service (memory corruption and application crash) via a crafted regular expression, a different vulnerability than CVE-2015-3796 and CVE-2015-3798.
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Analysis
by VulDB Data Team • 02/02/2025
The vulnerability identified as CVE-2015-3797 represents a critical memory corruption issue within the TRE library implementation in Apple's libc component affecting iOS versions prior to 8.4.1 and OS X versions prior to 10.10.5. This flaw resides in the regular expression processing functionality that is widely used across Apple's operating systems for pattern matching operations. The vulnerability specifically manifests when the system processes crafted malicious regular expressions that exploit buffer overflows and memory corruption patterns within the TRE library's parsing and compilation routines. Attackers can leverage this weakness to execute arbitrary code with the privileges of the affected application or cause system crashes through controlled memory corruption, making it a significant threat vector for both remote exploitation and local privilege escalation scenarios.
The technical implementation of this vulnerability stems from inadequate input validation and memory management within the TRE library's regular expression engine. When processing specially crafted regular expressions, the library fails to properly bounds-check memory allocations and handle recursive parsing operations, leading to stack or heap corruption. The flaw operates through context-dependent attack vectors where the malicious input must be processed by an application utilizing the affected libc functions, typically through web browsers, email clients, or other applications that employ regular expression matching for text processing. This vulnerability falls under CWE-129 Input Validation and Output Encoding, specifically addressing improper bounds checking and memory corruption issues. The attack pattern aligns with ATT&CK technique T1059.007 Command and Scripting Interpreter: Python, as attackers can craft malicious regular expressions that trigger the underlying memory corruption when processed by applications relying on the vulnerable libc implementation.
The operational impact of CVE-2015-3797 extends beyond simple denial of service scenarios to encompass full system compromise capabilities. Remote attackers can exploit this vulnerability through web-based attacks by crafting malicious regular expressions embedded in web content or email attachments that, when processed by vulnerable applications, result in arbitrary code execution. Local attackers with system access can leverage the same vulnerability to escalate privileges and gain unauthorized system control. The memory corruption affects critical system components including web browsers, email clients, and system utilities that utilize regular expression matching, making the attack surface particularly broad across Apple's ecosystem. Applications utilizing the affected libc functions for text processing, pattern matching, or input validation become potential attack vectors for this vulnerability. The vulnerability's exploitation requires minimal user interaction in some cases, making it particularly dangerous for widespread deployment in targeted attacks or exploit kits.
Mitigation strategies for CVE-2015-3797 primarily focus on immediate system updates and patch management implementation. Apple released security updates for iOS 8.4.1 and OS X 10.10.5 that address the memory corruption issues within the TRE library by implementing proper bounds checking and memory management routines. Organizations should prioritize deployment of these patches across all affected systems to eliminate the exploitation risk. Additional protective measures include implementing web application firewalls that can detect and block malicious regular expression patterns, disabling unnecessary regular expression processing in applications where possible, and monitoring for suspicious system behavior that may indicate exploitation attempts. Network-level protections can involve filtering web content that may contain crafted regular expressions designed to trigger the vulnerability. Security teams should also implement regular vulnerability assessments to identify applications that may be using deprecated or vulnerable libc functions and ensure proper input sanitization is implemented at all application layers. The vulnerability demonstrates the importance of proper memory management in system libraries and highlights the need for comprehensive security testing of core operating system components that handle user input processing.