CVE-2019-12652 in IOS
Summary
by MITRE
A vulnerability in the ingress packet processing function of Cisco IOS Software for Cisco Catalyst 4000 Series Switches could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition on an affected device. The vulnerability is due to improper resource allocation when processing TCP packets directed to the device on specific Cisco Catalyst 4000 Series Switches. An attacker could exploit this vulnerability by sending crafted TCP streams to an affected device. A successful exploit could cause the affected device to run out of buffer resources, impairing operations of control plane and management plane protocols, resulting in a DoS condition. This vulnerability can be triggered only by traffic that is destined to an affected device and cannot be exploited using traffic that transits an affected device.
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Analysis
by VulDB Data Team • 12/28/2023
The vulnerability identified as CVE-2019-12652 represents a critical denial of service weakness within Cisco IOS Software operating on Cisco Catalyst 4000 Series Switches. This flaw specifically targets the ingress packet processing function, creating a pathway for unauthenticated remote attackers to disrupt network operations without requiring any credentials or privileged access. The vulnerability exists in the manner in which the affected switches handle TCP packet processing, particularly when these packets are directed toward the device itself rather than passing through it. The Cisco Catalyst 4000 Series Switches are widely deployed in enterprise and data center environments, making this vulnerability particularly concerning as it could impact critical network infrastructure components that handle substantial traffic loads and support essential business operations.
The technical root cause of this vulnerability stems from improper resource allocation mechanisms within the control plane processing of TCP packets. When the switch receives specially crafted TCP streams, the ingress processing logic fails to properly manage buffer resources, leading to gradual consumption of available memory pools. This resource exhaustion occurs specifically during the handling of TCP packets destined for the device, where the switch's packet processing engine does not adequately validate or limit the allocation of buffer space for incoming connections. The vulnerability operates at the network layer where TCP packets are received and processed, making it distinct from other types of DoS attacks that might target application layer services or network protocols. According to CWE classification, this vulnerability maps to CWE-129, which describes improper validation of the length of input buffers, and CWE-131, which covers improper handling of length parameters. The attack vector requires that traffic be directed specifically to the vulnerable device, meaning that the switch must be the ultimate destination of the malicious packets rather than functioning as a transit point for traffic.
The operational impact of this vulnerability extends beyond simple network disruption, affecting critical control plane and management plane protocols that maintain device functionality and network visibility. When buffer resources become exhausted, the switch experiences degraded performance that can manifest as packet loss, increased latency, or complete service interruption. The DoS condition affects not only data plane operations but also the control plane functions responsible for routing decisions, management communications, and device monitoring capabilities. Network administrators may observe the switch becoming unresponsive to management commands, failing to process routing updates, or experiencing complete service outages. This vulnerability particularly impacts enterprise networks where Catalyst 4000 Series Switches serve as core infrastructure components, potentially causing cascading failures that affect multiple network segments. The attack can be executed remotely without authentication, making it especially dangerous as attackers can exploit this weakness from outside the network perimeter. According to ATT&CK framework, this vulnerability aligns with technique T1498, which covers network denial of service attacks, and T1071, which covers application layer protocol usage for command and control communications.
Mitigation strategies for CVE-2019-12652 should focus on both immediate defensive measures and long-term architectural improvements. Cisco has released patches and software updates that address the buffer allocation flaw in affected IOS versions, requiring network administrators to upgrade their switch firmware to versions containing the necessary fixes. Network segmentation and access control measures can help reduce the attack surface by limiting exposure of vulnerable switches to untrusted networks. Implementing rate limiting and packet filtering rules at network boundaries can help prevent malicious TCP streams from reaching the affected devices. Monitoring systems should be configured to detect unusual buffer usage patterns or sudden increases in packet processing activity that might indicate exploitation attempts. Network administrators should also consider implementing intrusion detection systems that can identify and alert on suspicious TCP traffic patterns targeting known vulnerable switch models. The vulnerability highlights the importance of maintaining current security patches and conducting regular vulnerability assessments of network infrastructure components. Organizations should also develop incident response procedures specifically addressing DoS conditions affecting core network switches, as these attacks can have significant business impact and require rapid response capabilities to restore normal network operations and maintain service availability.