CVE-2013-5140 in iOS
Summary
by MITRE
The kernel in Apple iOS before 7 allows remote attackers to cause a denial of service (assertion failure and device restart) via an invalid packet fragment.
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Analysis
by VulDB Data Team • 05/25/2021
The vulnerability identified as CVE-2013-5140 represents a critical kernel-level flaw in Apple iOS versions prior to 7.0, where the operating system fails to properly validate packet fragments during network processing. This issue stems from inadequate input sanitization within the kernel's network stack implementation, specifically affecting how the system handles malformed or invalid packet fragments that may be transmitted over network interfaces. The flaw manifests as an assertion failure that occurs when the kernel encounters unexpected packet fragmentation patterns, leading to immediate system instability and subsequent device restart.
This vulnerability operates at the core networking layer of the iOS kernel, leveraging the fundamental network packet processing mechanisms that handle internet protocol communication. When an attacker crafts and transmits a specially malformed packet fragment, the kernel's packet reassembly logic fails to properly validate the fragment structure, causing an assertion to trigger within the kernel code. The assertion failure represents a critical error condition that the kernel cannot gracefully handle, resulting in an immediate system crash and forced restart of the device. This behavior aligns with CWE-129, which describes improper validation of input boundaries, and specifically relates to improper handling of malformed network data within kernel space.
The operational impact of this vulnerability extends beyond simple denial of service, as it can be exploited remotely without requiring any user interaction or authentication. An attacker positioned on the same network segment or capable of routing malicious traffic can exploit this weakness by sending crafted packet fragments that trigger the kernel assertion failure. The device restart caused by this vulnerability effectively renders the iOS device temporarily unusable until manual intervention or automatic reboot occurs, creating significant disruption to device availability and user experience. This type of attack pattern falls under ATT&CK technique T1499.004, which describes network denial of service attacks targeting system resources.
The exploitation of CVE-2013-5140 demonstrates a classic kernel-level buffer over-read vulnerability where the system fails to properly validate packet fragment boundaries before processing them. The vulnerability affects all iOS versions before 7.0, indicating a long-standing issue within the kernel's network processing code that was not properly addressed until the iOS 7 release. This flaw represents a fundamental security gap in the kernel's packet validation logic, where the system assumes valid packet structures without sufficient verification mechanisms. The assertion failure occurs during the packet reassembly phase, where the kernel attempts to reconstruct fragmented packets from their constituent parts, making this vulnerability particularly dangerous as it can be triggered through normal network traffic processing.
Mitigation strategies for this vulnerability primarily involve updating to iOS 7.0 or later versions where Apple implemented proper packet fragment validation and improved kernel error handling mechanisms. System administrators and users should prioritize immediate patching to address this vulnerability, as the remote exploitation capability makes it particularly dangerous in networked environments. Network-level protections such as intrusion detection systems that monitor for unusual packet fragmentation patterns may provide additional defense-in-depth, though the most effective mitigation remains the application of Apple's security patches. The vulnerability highlights the importance of proper kernel validation mechanisms and demonstrates how seemingly minor input validation issues can lead to complete system compromise through denial of service attacks.