CVE-2017-12232 in IOS
Summary
by MITRE
A vulnerability in the implementation of a protocol in Cisco Integrated Services Routers Generation 2 (ISR G2) Routers running Cisco IOS 15.0 through 15.6 could allow an unauthenticated, adjacent attacker to cause an affected device to reload, resulting in a denial of service (DoS) condition. The vulnerability is due to a misclassification of Ethernet frames. An attacker could exploit this vulnerability by sending a crafted Ethernet frame to an affected device. A successful exploit could allow the attacker to cause the affected device to reload, resulting in a DoS condition. Cisco Bug IDs: CSCvc03809.
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Analysis
by VulDB Data Team • 09/09/2024
The vulnerability identified as CVE-2017-12232 affects Cisco Integrated Services Routers Generation 2 (ISR G2) devices running Cisco IOS version 15.0 through 15.6, representing a significant denial of service weakness that impacts network infrastructure reliability. This flaw manifests in the protocol implementation of the affected routers, specifically within their Ethernet frame processing mechanisms, creating a pathway for unauthorized disruption of critical network services. The vulnerability's classification as a network infrastructure weakness places it squarely within the domain of operational technology security where device availability directly impacts business continuity and network operations. The affected devices are particularly susceptible because they process Ethernet frames without proper validation of frame characteristics that could trigger system instability.
The technical root cause of this vulnerability stems from a misclassification of Ethernet frames within the router's processing pipeline, where the system fails to properly validate or handle specific frame structures that could cause unexpected behavior in the underlying operating system. This misclassification occurs during the frame reception and processing phase, where the router's IOS software incorrectly interprets certain Ethernet frame parameters, leading to a system state that triggers an automatic device reload. The flaw demonstrates a classic buffer handling or frame parsing vulnerability where malformed input data causes the system to enter an unrecoverable state, resulting in the device rebooting automatically. The specific nature of the misclassification suggests an insufficient validation mechanism in the frame processing code, potentially related to frame length fields, protocol identifiers, or header structures that are not properly sanitized before system processing.
An attacker exploiting this vulnerability requires physical or logical adjacency to the affected device, meaning they must be in a position to send Ethernet frames directly to the router's interfaces, typically through a local network segment or by utilizing network access points that provide direct connection to the device. The attack vector is classified as adjacent network access, which aligns with the Common Weakness Enumeration (CWE) category CWE-20, representing "Improper Input Validation" in network protocol implementations. Successful exploitation of this vulnerability results in an immediate denial of service condition where the affected router automatically reboots, disrupting network connectivity and potentially causing cascading failures in network infrastructure that depends on these devices for routing and forwarding services. The impact extends beyond simple service interruption as network administrators must respond to the device reload, potentially causing service degradation while the router reinitializes and reestablishes network connections.
The operational impact of CVE-2017-12232 creates substantial risk for organizations relying on Cisco ISR G2 routers for network infrastructure, as these devices often serve as core routing points in enterprise and service provider networks. The automatic reload behavior effectively provides an attacker with a reliable method to disrupt network services without requiring authentication credentials or complex attack chains, making this vulnerability particularly dangerous in environments where physical security controls may be insufficient. Network resilience is significantly compromised as the DoS condition can occur without detection, potentially allowing repeated attacks that keep the device in a continuous reload cycle, effectively rendering the router unusable. This vulnerability also impacts the broader network ecosystem as routing disruptions can affect multiple services and applications that depend on stable network connectivity, potentially causing extended outages that extend beyond the immediate device affected.
Cisco has addressed this vulnerability through specific software releases and security advisories that include patches to correct the Ethernet frame processing logic and implement proper frame validation mechanisms. Organizations should prioritize applying the relevant IOS software updates that contain fixes for CSCvc03809, as these patches directly address the misclassification issue in the frame handling code. Network administrators should implement monitoring solutions to detect unusual reload patterns that might indicate exploitation attempts, while also reviewing network access controls to limit physical or logical access to affected devices. The vulnerability's characteristics align with ATT&CK technique T1499.002, "Endpoint Denial of Service," where attackers target network infrastructure devices to create service disruptions, making it essential for security teams to understand how this vulnerability fits into broader attack patterns targeting network availability. Organizations should also consider implementing network segmentation strategies to limit the impact of potential exploitation attempts and ensure that critical network infrastructure devices are protected through layered security controls that include both physical and logical access restrictions.