CVE-2014-3308 in IOS XE
Summary
by MITRE
Cisco IOS XR on Trident line cards in ASR 9000 devices lacks a static punt policer, which allows remote attackers to cause a denial of service (CPU consumption) by sending many crafted packets, aka Bug ID CSCun83985.
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Analysis
by VulDB Data Team • 02/08/2022
Cisco IOS XR running on Trident line cards within ASR 9000 devices contains a critical design flaw that manifests as the absence of a static punt policer mechanism. This vulnerability enables remote attackers to execute denial of service attacks by transmitting carefully crafted packets that overwhelm the device's CPU resources. The flaw specifically affects the packet processing behavior when packets are punted from the hardware forwarding plane to the software control plane, creating a scenario where malicious traffic can cause excessive CPU utilization and ultimately lead to device instability or complete service disruption.
The technical implementation of this vulnerability stems from the lack of rate limiting mechanisms within the IOS XR software stack on Trident line cards. When packets arrive that require processing in the software control plane, the system does not enforce any predetermined limits on the rate at which these packets can be punted to the CPU. This absence of policing creates an exploitable condition where an attacker can flood the device with packets that trigger the punt mechanism, causing the CPU to become saturated with processing tasks that are typically reserved for legitimate control plane operations. The vulnerability is classified under CWE-116 as improper handling of synchronous execution flow, where the system fails to properly manage concurrent processing tasks that should be limited to prevent resource exhaustion.
The operational impact of this vulnerability extends beyond simple service disruption to potentially compromise network availability and reliability. Attackers can exploit this weakness to consume CPU cycles at an unsustainable rate, leading to degraded performance, increased latency, or complete device failure. Network operators may experience cascading effects where the compromised device affects routing stability and connectivity throughout the network infrastructure. The vulnerability affects all versions of Cisco IOS XR software running on Trident line cards within ASR 9000 devices, making it particularly concerning for large-scale deployments where these devices serve as critical core network components. The attack vector is remote, meaning that adversaries do not require physical access or network credentials to exploit the vulnerability, significantly increasing the attack surface and potential impact.
Mitigation strategies for this vulnerability should focus on implementing proper rate limiting and policing mechanisms within the network infrastructure. Network administrators should consider applying Cisco's recommended software patches and updates that introduce the missing static punt policer functionality. Additionally, implementing ingress filtering and rate limiting at network boundaries can help reduce the volume of malicious packets reaching the vulnerable devices. The implementation of monitoring solutions that can detect unusual CPU utilization patterns and automated alerting mechanisms provides early warning capabilities for potential exploitation attempts. Organizations should also consider network segmentation strategies to isolate critical devices and limit the potential impact of successful attacks. This vulnerability aligns with ATT&CK technique T1498 which covers resource exhaustion attacks, and represents a classic example of how insufficient input validation and rate limiting can create security weaknesses in network infrastructure devices.