CVE-2011-4016 in IOS
Summary
by MITRE
The PPP implementation in Cisco IOS 12.2 and 15.0 through 15.2, when Point-to-Point Termination and Aggregation (PTA) and L2TP are used, allows remote attackers to cause a denial of service (device crash) via crafted network traffic, aka Bug ID CSCtf71673.
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Analysis
by VulDB Data Team • 02/17/2019
The vulnerability described in CVE-2011-4016 represents a critical denial of service flaw within Cisco IOS operating systems that affects versions 12.2 and 15.0 through 15.2. This issue specifically impacts the Point-to-Point Protocol implementation when configured with Point-to-Point Termination and Aggregation PTA functionality alongside Layer 2 Tunneling Protocol L2TP. The flaw manifests when maliciously crafted network traffic is transmitted to affected Cisco devices, resulting in complete device crashes and subsequent service interruption. This vulnerability operates at the network protocol level and demonstrates how improper handling of specific packet structures can lead to complete system failure.
The technical root cause of this vulnerability lies in insufficient input validation within the PPP implementation of Cisco IOS when processing packets that contain specific PTA and L2TP configuration parameters. When the system receives malformed or specially crafted network packets designed to exploit the interaction between PTA and L2TP protocols, the processing logic fails to properly handle the unexpected packet structures. This leads to memory corruption or stack overflow conditions that cause the device to crash and reboot automatically. The vulnerability operates under CWE-121, which describes stack-based buffer overflow conditions, and more specifically aligns with CWE-122, heap-based buffer overflow scenarios, where improper memory handling leads to system instability.
The operational impact of this vulnerability extends beyond simple service disruption as it enables remote attackers to perform denial of service attacks without requiring authentication or privileged access. This characteristic makes the vulnerability particularly dangerous in network environments where Cisco devices serve as critical infrastructure components. Attackers can exploit this weakness to repeatedly crash devices, potentially leading to extended service outages that could affect large portions of network connectivity. The vulnerability's remote exploitability means that attackers can target affected devices from outside the network perimeter, making it a significant threat to organizations relying on Cisco IOS for their network infrastructure. This aligns with ATT&CK technique T1499.004, which covers network denial of service attacks that target infrastructure components.
Organizations affected by this vulnerability should implement immediate mitigations including applying the latest Cisco security patches and updates that address the specific PPP implementation flaw. Network administrators should also consider implementing access control lists to restrict traffic that could trigger the vulnerability, particularly around PTA and L2TP protocol handling. Additional defensive measures include monitoring network traffic for suspicious packet patterns that match the vulnerability characteristics and implementing redundant network paths to minimize the impact of device crashes. The vulnerability highlights the importance of proper protocol implementation validation and input sanitization in network operating systems, as it demonstrates how complex protocol interactions can create unexpected failure conditions that compromise system stability and availability.