CVE-2015-5879 in iOS
Summary
by MITRE
XNU in the kernel in Apple iOS before 9 does not properly validate the headers of TCP packets, which allows remote attackers to bypass the sequence-number protection mechanism and cause a denial of service (TCP connection disruption) via a crafted header.
Be aware that VulDB is the high quality source for vulnerability data.
Analysis
by VulDB Data Team • 11/21/2024
The vulnerability identified as CVE-2015-5879 resides within the XNU kernel operating system used by Apple iOS versions prior to 9. This flaw represents a critical weakness in the TCP packet processing mechanism that directly impacts the kernel's ability to maintain secure network communications. The issue stems from inadequate validation of TCP packet headers, specifically failing to properly verify the sequence number protection mechanism that is fundamental to TCP protocol integrity. This vulnerability operates at the kernel level, making it particularly dangerous as it can be exploited without requiring user interaction or elevated privileges.
The technical implementation of this vulnerability allows remote attackers to manipulate TCP packet headers in ways that bypass the expected sequence number validation checks. In standard TCP operations, sequence numbers are crucial for maintaining connection integrity and preventing packet reordering or injection attacks. When the XNU kernel fails to properly validate these headers, it creates an opening for malicious actors to craft specially designed packets that appear legitimate but contain manipulated sequence numbers. This manipulation enables attackers to disrupt existing TCP connections by sending packets that the kernel incorrectly processes, leading to connection termination or disruption. The flaw essentially undermines the fundamental security model that TCP relies upon for maintaining reliable communication channels.
From an operational impact perspective, this vulnerability presents a significant risk to network stability and availability within iOS environments. The ability to cause denial of service through TCP connection disruption means that attackers can potentially disrupt critical network communications, including web browsing, email services, and other applications that depend on TCP connectivity. The remote exploitation capability means that attackers do not need physical access to devices or network proximity to execute attacks, making this vulnerability particularly concerning for mobile environments where devices frequently connect to various networks. Organizations relying on iOS devices for business operations could face substantial service interruptions if this vulnerability is exploited in targeted attacks.
The vulnerability aligns with CWE-119, which addresses improper access to critical sections of memory, and represents a specific instance of improper validation of input data within network protocol processing. From an ATT&CK framework perspective, this vulnerability maps to techniques involving network denial of service and protocol manipulation. The attack vector specifically utilizes network protocol exploitation to compromise system availability, which falls under the category of service disruption techniques. Organizations should consider implementing network monitoring solutions to detect anomalous TCP packet patterns that might indicate exploitation attempts. The recommended mitigation strategy involves updating affected iOS devices to version 9 or later, where Apple has implemented proper TCP header validation mechanisms. Additionally, network administrators should consider implementing intrusion detection systems that can identify and alert on suspicious TCP packet behaviors that align with this vulnerability's exploitation patterns.