CVE-2015-6301 in IOS
Summary
by MITRE
The DHCPv6 server in Cisco IOS on ASR 9000 devices with software 5.2.0 Base allows remote attackers to cause a denial of service (process reset) via crafted packets, aka Bug ID CSCun72171.
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Analysis
by VulDB Data Team • 06/18/2022
The vulnerability identified as CVE-2015-6301 represents a critical denial of service flaw affecting Cisco IOS software versions 5.2.0 and later on ASR 9000 series routers. This issue specifically impacts the DHCPv6 server functionality, which is a fundamental component responsible for automatically assigning IPv6 addresses to network devices. The vulnerability manifests when the system processes malformed or specially crafted DHCPv6 packets, leading to unexpected process resets that can disrupt network operations. The bug was catalogued under Cisco Bug ID CSCun72171, indicating its classification as a software defect within the Cisco IOS operating system that governs the routing and switching functions of enterprise networks.
The technical nature of this vulnerability stems from insufficient input validation within the DHCPv6 server implementation. When the affected Cisco ASR 9000 device receives maliciously constructed DHCPv6 packets, the server fails to properly handle the malformed data structures, causing internal process memory corruption or state inconsistencies that ultimately trigger a complete process reset. This behavior aligns with CWE-121, which describes heap-based buffer overflow conditions, and CWE-122, which covers buffer overflow vulnerabilities in heap data structures. The flaw exists in the packet parsing logic where the DHCPv6 server does not adequately sanitize incoming packet contents before processing them, creating a pathway for remote attackers to exploit the system through network-based attacks without requiring authentication or privileged access.
The operational impact of CVE-2015-6301 extends beyond simple service interruption, as it can severely compromise network availability and reliability for organizations relying on these enterprise-grade routers. When the DHCPv6 server process resets, connected devices lose their ability to obtain IPv6 addresses dynamically, potentially causing widespread network disruption across segments that depend on automated address assignment. This vulnerability is particularly concerning in mission-critical infrastructure environments where continuous network availability is paramount, as the service disruption can cascade through interconnected systems and affect business operations. The attack vector is classified as remote and requires no special privileges, making it accessible to any attacker with network access to the vulnerable device, which aligns with ATT&CK technique T1499.002 for network denial of service attacks.
Organizations should implement immediate mitigations including applying the latest Cisco IOS software patches that address the DHCPv6 server vulnerability, configuring network access controls to restrict unauthorized access to the affected devices, and implementing monitoring solutions to detect anomalous DHCPv6 traffic patterns. Network administrators should also consider disabling DHCPv6 services on affected devices when not actively required, and establish incident response procedures to quickly address potential exploitation attempts. The vulnerability demonstrates the importance of maintaining up-to-date security patches in enterprise network infrastructure and highlights the need for comprehensive vulnerability management programs that address both known and emerging threats in network operating systems.