CVE-2015-5869 in Watch
Summary
by MITRE
The Neighbor Discovery (ND) protocol implementation in the IPv6 stack in Apple iOS before 9 allows remote attackers to reconfigure a hop-limit setting via a small hop_limit value in a Router Advertisement (RA) message.
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Analysis
by VulDB Data Team • 11/21/2024
The vulnerability described in CVE-2015-5869 represents a critical flaw in the IPv6 Neighbor Discovery protocol implementation within Apple iOS versions prior to 9. This issue stems from insufficient validation of hop-limit values in Router Advertisement messages, creating a pathway for remote attackers to manipulate network configuration parameters. The Neighbor Discovery protocol serves as a fundamental component of IPv6 networks, responsible for address resolution, router discovery, and network configuration management. When a device receives a Router Advertisement message, it typically updates its routing tables and network parameters based on the information provided by the router. The flaw occurs because the iOS implementation fails to properly validate the hop_limit field in incoming RA messages, allowing malicious actors to craft specially crafted packets with intentionally small hop_limit values that can override legitimate network settings.
This vulnerability operates at the network layer of the TCP/IP stack and specifically targets the IPv6 implementation within Apple's mobile operating system. The hop_limit field in IPv6 packets serves a similar function to the TTL (Time To Live) field in IPv4, determining how many hops a packet can traverse before being discarded. When an attacker sends a Router Advertisement message with an abnormally low hop_limit value, the vulnerable iOS device may accept this configuration, potentially causing network traffic to be prematurely dropped or redirecting traffic through unintended paths. The attack vector is particularly concerning because it requires no local access or authentication, making it a classic example of a remote code execution or privilege escalation vulnerability within network protocols. According to CWE-20, this represents a weakness in input validation where the system fails to properly validate the range or value of hop_limit parameters in received network messages.
The operational impact of this vulnerability extends beyond simple network disruption, as it can enable more sophisticated attacks such as man-in-the-middle scenarios or network partitioning. An attacker could leverage this flaw to effectively isolate specific network segments or redirect traffic through malicious nodes, potentially compromising network integrity and availability. The vulnerability affects all Apple iOS devices running versions prior to iOS 9, making it particularly widespread given the large installed base of affected devices. From an ATT&CK framework perspective, this vulnerability aligns with techniques involving protocol manipulation and network configuration modification, specifically mapping to T1071.004 for Application Layer Protocol: DNS and T1562.001 for Impair Command and Control. The attack could potentially be combined with other network-based exploits to create more comprehensive compromise scenarios, as network configuration changes often serve as prerequisites for deeper system exploitation.
Mitigation strategies for this vulnerability include immediate deployment of iOS 9 updates, which properly validate hop_limit values in Router Advertisement messages and prevent unauthorized configuration changes. Network administrators should also implement additional monitoring of Router Advertisement traffic to detect anomalous hop_limit values and consider deploying firewall rules that limit the acceptance of RA messages from untrusted sources. The vulnerability highlights the importance of proper input validation in network protocol implementations and serves as a reminder of the critical security considerations that must be addressed in IPv6 stack implementations. Organizations should also consider implementing network segmentation and access controls to limit the potential impact of such vulnerabilities, while maintaining awareness of similar issues in other network protocol implementations that may present analogous risks.