CVE-2015-6278 in IOS
Summary
by MITRE
The IPv6 snooping functionality in the first-hop security subsystem in Cisco IOS 12.2, 15.0, 15.1, 15.2, 15.3, 15.4, and 15.5 and IOS XE 3.2SE, 3.3SE, 3.3XO, 3.4SG, 3.5E, and 3.6E before 3.6.3E; 3.7E before 3.7.2E; 3.9S and 3.10S before 3.10.6S; 3.11S before 3.11.4S; 3.12S and 3.13S before 3.13.3S; and 3.14S before 3.14.2S does not properly implement the Control Plane Protection (aka CPPr) feature, which allows remote attackers to cause a denial of service (device reload) via a flood of ND packets, aka Bug ID CSCus19794.
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Analysis
by VulDB Data Team • 06/19/2022
The vulnerability described in CVE-2015-6278 represents a critical flaw in Cisco IOS and IOS XE network operating systems that affects the IPv6 neighbor discovery (ND) packet processing functionality within the first-hop security subsystem. This issue specifically targets the Control Plane Protection mechanism implementation, which is designed to protect network devices from excessive traffic that could overwhelm their control plane resources. The flaw exists across multiple IOS versions including 12.2, 15.0 through 15.5, and various IOS XE releases from 3.2SE through 3.14S, with affected versions prior to the specified patch releases. The vulnerability enables remote attackers to exploit the insufficient validation and rate limiting of IPv6 neighbor discovery messages, creating a pathway for denial of service attacks that can ultimately force device reloads.
The technical implementation flaw stems from the improper handling of neighbor discovery packets within the control plane protection framework, which is categorized under CWE-20 as "Improper Input Validation" and CWE-1333 as "Improper Restriction of a Control Flow Variable." When the system receives a flood of neighbor discovery packets, the insufficient validation mechanisms fail to properly rate limit or filter these packets, allowing malicious actors to overwhelm the device's processing capabilities. The attack vector involves sending a high volume of ND packets to a targeted device, exploiting the weakness in the first-hop security subsystem where these packets should be properly monitored and controlled. This flaw essentially bypasses the intended protection mechanisms that should limit the rate of control plane traffic, leaving the device vulnerable to resource exhaustion attacks.
The operational impact of this vulnerability is severe and directly affects network availability and reliability. When exploited, the vulnerability can cause complete device reloads, effectively taking the network infrastructure offline until manual intervention occurs. This type of denial of service attack can be particularly damaging in enterprise and service provider environments where network uptime is critical for business operations. The attack requires minimal privileges and can be executed remotely, making it particularly dangerous as it can be launched from any location with network access to the targeted device. The vulnerability affects network devices that are configured to use IPv6 neighbor discovery functionality, which is commonly enabled in modern network environments that support IPv6 protocols. According to ATT&CK framework, this vulnerability maps to T1499.004 as "Endpoint Denial of Service" and T1562.001 as "Impairing Defenses" since it specifically targets the device's ability to process control plane traffic and maintain operational integrity.
Mitigation strategies for this vulnerability require immediate patching of affected IOS and IOS XE versions to the specified secure releases, with particular attention to the control plane protection configuration. Network administrators should implement rate limiting and access control lists specifically targeting neighbor discovery traffic to prevent excessive packet flooding. The recommended approach includes configuring appropriate traffic rate limits for IPv6 neighbor discovery messages and implementing monitoring to detect unusual patterns of ND packet generation. Additionally, organizations should consider disabling IPv6 neighbor discovery functionality on devices where it is not required, and implementing network segmentation to limit the potential impact of such attacks. The vulnerability also highlights the importance of regular security updates and proper network device configuration management, as outlined in NIST SP 800-53 controls related to system and information integrity. Organizations should conduct vulnerability assessments to identify all affected devices and prioritize remediation efforts based on network criticality and attack surface exposure.