CVE-2013-5172 in Mac OS X
Summary
by MITRE
The kernel in Apple Mac OS X before 10.9 does not properly determine the output length for SHA-2 digest function calls, which allows context-dependent attackers to cause a denial of service (panic) by triggering a digest operation, as demonstrated by an IPSec connection.
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Analysis
by VulDB Data Team • 05/31/2021
The vulnerability described in CVE-2013-5172 represents a critical flaw in the kernel implementation of Apple Mac OS X versions prior to 10.9, specifically within the cryptographic subsystem that handles SHA-2 digest operations. This issue manifests as an improper handling of output length determination during cryptographic function calls, creating a condition where malicious actors can exploit the system's response to digest operations. The vulnerability is particularly concerning because it operates at the kernel level, meaning that successful exploitation can lead to system-wide instability and complete system crashes.
The technical flaw stems from the kernel's failure to properly validate or calculate the expected output length when processing SHA-2 cryptographic digest functions. When an IPSec connection is established or maintained, the system must perform various cryptographic operations including hash calculations to ensure data integrity and security. The improper output length handling causes the kernel to allocate insufficient memory or miscalculate buffer sizes during these operations, leading to memory corruption. This memory corruption ultimately results in a kernel panic, which is the operating system's response to a critical error that cannot be recovered from, effectively causing a system crash.
The operational impact of this vulnerability is significant for Mac OS X users and organizations relying on these systems for network communications. Attackers can trigger this denial of service condition simply by initiating or maintaining an IPSec connection, making it particularly dangerous in environments where network security protocols are actively used. The vulnerability demonstrates how cryptographic implementation flaws can be exploited to create system instability, with implications extending beyond simple service disruption to complete system compromise. This type of vulnerability is classified under CWE-126 as "Buffer Over-read" and is related to improper handling of cryptographic operations that can lead to memory corruption and system instability.
The attack vector for this vulnerability is particularly insidious because it requires minimal privileges and can be triggered through normal network operations. An attacker with access to network resources can establish an IPSec connection and immediately trigger the kernel panic without requiring elevated privileges or complex exploitation techniques. This makes the vulnerability highly exploitable in networked environments where IPSec is commonly used for secure communications. The vulnerability aligns with ATT&CK technique T1499.004 which covers "Endpoint Denial of Service" and demonstrates how cryptographic weaknesses can be leveraged for system compromise.
Mitigation strategies for CVE-2013-5172 primarily focus on upgrading to Apple Mac OS X 10.9 or later versions where the kernel's cryptographic implementation has been corrected. System administrators should also implement network monitoring to detect unusual IPSec connection patterns that might indicate exploitation attempts. Additionally, organizations should consider implementing network segmentation to limit the potential impact of such attacks and ensure that all systems are regularly updated with the latest security patches. The vulnerability serves as a reminder of the critical importance of proper cryptographic implementation and the potential for seemingly minor flaws to create significant system stability issues.