CVE-2011-2391 in Mac OS X
Summary
by MITRE
The IPv6 implementation in the kernel in Apple iOS before 7 allows remote attackers to cause a denial of service (CPU consumption) via crafted ICMPv6 packets.
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Analysis
by VulDB Data Team • 03/07/2022
The vulnerability identified as CVE-2011-2391 represents a critical denial of service weakness within Apple iOS kernel's IPv6 implementation. This flaw specifically affects iOS versions prior to version 7, creating a scenario where remote attackers can exploit the system through carefully crafted ICMPv6 packets to consume excessive CPU resources. The vulnerability stems from insufficient input validation and processing of ICMPv6 messages within the kernel's network stack, particularly in how the system handles certain malformed or specially constructed packets that trigger inefficient processing loops or resource allocation patterns.
The technical nature of this vulnerability aligns with CWE-129, which describes improper validation of input boundaries, and CWE-400, which covers unspecified resource management issues. The flaw operates at the kernel level where ICMPv6 packets are processed, allowing attackers to send malicious packets that cause the iOS device to enter into resource-intensive processing states. When these crafted packets arrive, the kernel's IPv6 implementation fails to properly validate or limit the processing of certain packet attributes, leading to excessive CPU utilization as the system attempts to handle malformed data structures or infinite loops in packet processing logic. This behavior creates a condition where legitimate network operations become impaired or completely halted due to the overwhelming CPU consumption.
The operational impact of this vulnerability extends beyond simple service disruption, as it can affect the overall stability and responsiveness of iOS devices. Mobile devices running affected iOS versions become vulnerable to attacks that can render them unusable or significantly degraded, particularly in environments where network connectivity is essential for device functionality. Attackers can exploit this vulnerability remotely without requiring authentication or physical access, making it particularly dangerous in mobile environments where devices are frequently exposed to untrusted networks. The resource consumption pattern typically manifests as sustained high CPU usage, potentially leading to device overheating, rapid battery drain, and complete system unresponsiveness, effectively creating a denial of service condition that can persist until the device is manually restarted or the malicious packets cease being transmitted.
Mitigation strategies for CVE-2011-2391 primarily focus on updating to iOS version 7 or later, which contains the necessary kernel-level patches addressing the ICMPv6 processing flaws. System administrators and users should prioritize immediate deployment of the official Apple security updates that contain the corrected IPv6 implementation. Network administrators can implement additional protective measures such as ICMPv6 filtering rules at network boundaries to block suspicious packets, though this approach provides only partial protection since the vulnerability exists within the kernel itself. The mitigation approach aligns with standard cybersecurity practices outlined in the ATT&CK framework under the T1499 category for network denial of service, emphasizing the need for both endpoint patching and network-level controls. Organizations should also consider implementing network monitoring to detect unusual CPU consumption patterns that might indicate exploitation attempts, and establish incident response procedures for handling potential denial of service events targeting mobile devices.