CVE-2017-12238 in IOS
Summary
by MITRE
A vulnerability in the Virtual Private LAN Service (VPLS) code of Cisco IOS 15.0 through 15.4 for Cisco Catalyst 6800 Series Switches could allow an unauthenticated, adjacent attacker to cause a C6800-16P10G or C6800-16P10G-XL type line card to crash, resulting in a denial of service (DoS) condition. The vulnerability is due to a memory management issue in the affected software. An attacker could exploit this vulnerability by creating a large number of VPLS-generated MAC entries in the MAC address table of an affected device. A successful exploit could allow the attacker to cause a C6800-16P10G or C6800-16P10G-XL type line card to crash, resulting in a DoS condition. This vulnerability affects Cisco Catalyst 6800 Series Switches that are running a vulnerable release of Cisco IOS Software and have a Cisco C6800-16P10G or C6800-16P10G-XL line card in use with Supervisor Engine 6T. To be vulnerable, the device must also be configured with VPLS and the C6800-16P10G or C6800-16P10G-XL line card needs to be the core-facing MPLS interfaces. Cisco Bug IDs: CSCva61927.
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Analysis
by VulDB Data Team • 07/30/2025
The vulnerability described in CVE-2017-12238 represents a critical memory management flaw within the Virtual Private LAN Service implementation of Cisco IOS software affecting specific Catalyst 6800 Series Switches. This issue manifests in the form of a denial of service condition that can be triggered by an unauthenticated attacker positioned in an adjacent network segment. The vulnerability specifically targets line card models C6800-16P10G and C6800-16P10G-XL when operating with Supervisor Engine 6T, making it particularly concerning for network infrastructure administrators responsible for maintaining high availability services.
The technical root cause of this vulnerability lies in improper memory handling within the VPLS code module of the affected IOS releases ranging from version 15.0 through 15.4. When an attacker generates an excessive number of MAC entries through VPLS operations, the system's memory management mechanisms fail to properly handle this resource exhaustion, leading to a complete system crash of the affected line card. This memory management failure creates a condition where legitimate network traffic cannot be processed properly, resulting in the denial of service state that impacts all services relying on that specific line card functionality. The vulnerability operates at the data link layer through MAC address table manipulation, making it particularly insidious as it can be exploited without requiring authentication credentials.
The operational impact of this vulnerability extends beyond simple service disruption, as it can affect the entire network infrastructure depending on the deployment architecture. When the targeted line card crashes, it can result in complete loss of connectivity for all services utilizing that particular hardware configuration, potentially affecting multiple network segments depending on how the VPLS services are implemented. The attack vector requires physical adjacency to the network, which reduces the attack surface but does not eliminate the risk entirely, as adjacent network segments may be compromised through various social engineering or network access methods. Network administrators must consider that this vulnerability can be exploited by insiders or attackers who have gained access to adjacent network segments, making it a significant concern for network security teams.
Mitigation strategies for this vulnerability should focus on immediate software updates and configuration changes to prevent exploitation. Cisco has released patches addressing this specific memory management issue through IOS software updates, and administrators should prioritize applying these patches to all affected devices. Additionally, network segmentation and access control measures should be implemented to limit the attack surface by restricting physical access to network equipment. The vulnerability aligns with CWE-129, which addresses improper validation of array indices, and can be mapped to ATT&CK technique T1499.004 for network denial of service attacks. Network monitoring should be enhanced to detect unusual MAC address table growth patterns that might indicate exploitation attempts, and regular vulnerability assessments should be conducted to identify similar memory management issues in other network infrastructure components.