CVE-2013-5174 in Mac OS X
Summary
by MITRE
Integer signedness error in the kernel in Apple Mac OS X before 10.9 allows local users to cause a denial of service (system crash) via a crafted tty read operation.
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Analysis
by VulDB Data Team • 05/31/2021
The vulnerability identified as CVE-2013-5174 represents a critical integer signedness error within the kernel of Apple Mac OS X operating systems prior to version 10.9. This flaw exists in the terminal device driver implementation where the system fails to properly handle signed integer comparisons during tty read operations. The issue stems from improper validation of integer values when processing terminal input, creating a scenario where maliciously crafted input can trigger unexpected behavior in the kernel's memory management subsystem. Such vulnerabilities fall under the CWE-191 category of Integer Underflow or Wraparound, which specifically addresses conditions where signed integers are not properly validated during arithmetic operations. The vulnerability demonstrates a classic example of how improper input validation can lead to system instability and denial of service conditions.
The technical exploitation of this vulnerability occurs when a local attacker crafts a specific tty read operation that manipulates signed integer values in a way that causes the kernel to perform invalid memory operations. When the kernel processes this crafted input, the signed integer underflow results in memory corruption or invalid memory access patterns that ultimately lead to system crashes. The vulnerability is particularly concerning because it requires only local user privileges to exploit, making it accessible to any user with login access to the affected system. The attack vector specifically targets the terminal driver subsystem where the kernel handles input/output operations for serial terminals and pseudo-terminals, which are fundamental components of the operating system's user interface and command execution environment.
The operational impact of CVE-2013-5174 extends beyond simple denial of service to potentially compromise the stability and availability of the entire operating system. System crashes resulting from this vulnerability can occur at any time during normal operation, making the affected system unreliable for both personal and enterprise use. The vulnerability affects all versions of Mac OS X prior to 10.9, which includes a significant portion of deployed systems that may not have received timely updates. From an attacker perspective, this vulnerability aligns with the ATT&CK technique of privilege escalation through system instability, where local users can leverage kernel-level flaws to cause system-wide disruptions. The lack of proper input sanitization in the kernel's terminal handling code creates a persistent risk that can be exploited repeatedly until the underlying issue is addressed through system updates.
Mitigation strategies for CVE-2013-5174 primarily focus on immediate system updates to Apple Mac OS X 10.9 or later versions where the vulnerability has been patched. System administrators should prioritize patch deployment across all affected devices to prevent exploitation, as the vulnerability does not require network access or special privileges beyond local user access. Additionally, organizations should implement monitoring for unusual system crash patterns that might indicate exploitation attempts, though such monitoring would be limited since the vulnerability is designed to cause system instability rather than provide persistent access. The fix implemented by Apple addresses the integer signedness error in the kernel's terminal driver by ensuring proper validation of integer values during tty read operations, preventing the underflow condition that led to system crashes. Security teams should also consider implementing access controls that limit local user privileges where possible, as this reduces the attack surface for local exploitation attempts. The vulnerability serves as a reminder of the importance of kernel-level input validation and proper integer handling in operating system security design, particularly in components that handle user input directly.