CVE-2017-12211 in IOS
Summary
by MITRE
A vulnerability in the IPv6 Simple Network Management Protocol (SNMP) code of Cisco IOS and Cisco IOS XE Software could allow an authenticated, remote attacker to cause high CPU usage or a reload of the device. The vulnerability is due to IPv6 sub block corruption. An attacker could exploit this vulnerability by polling the affected device IPv6 information. An exploit could allow the attacker to trigger high CPU usage or a reload of the device. Known Affected Releases: Denali-16.3.1. Cisco Bug IDs: CSCvb14640.
Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.
Analysis
by VulDB Data Team • 01/11/2021
The vulnerability identified as CVE-2017-12211 represents a critical flaw in the IPv6 Simple Network Management Protocol implementation within Cisco IOS and IOS XE software versions. This security issue stems from improper handling of IPv6 sub block corruption during SNMP polling operations, creating a potential vector for authenticated remote attackers to disrupt network device operations. The vulnerability specifically affects Cisco IOS releases including the Denali-16.3.1 branch, where the SNMP processing code fails to properly validate IPv6 address structures during management queries. The flaw manifests when an attacker with valid credentials performs SNMP polling operations targeting IPv6 network information, triggering a cascade of CPU-intensive processing that can ultimately lead to device instability.
The technical exploitation of this vulnerability occurs through the manipulation of IPv6 address structures within SNMP responses, where the corrupted sub block data causes the device's CPU utilization to spike dramatically. This condition can persist until the device either reaches a critical load threshold or requires manual intervention to restore normal operations. The root cause lies in the insufficient input validation mechanisms within the SNMP IPv6 processing code, which fails to properly sanitize or reject malformed IPv6 sub block data during polling operations. This weakness creates a denial of service scenario where legitimate network management activities become weaponized to exhaust system resources and potentially force device reboots.
The operational impact of CVE-2017-12211 extends beyond simple service disruption, as it represents a significant threat to network availability and stability. Network administrators face the risk of unauthorized actors leveraging this vulnerability to perform sustained denial of service attacks against critical infrastructure devices, potentially affecting network monitoring, management, and overall operational continuity. The vulnerability's authenticated nature means that only users with valid credentials can exploit it, but this requirement does not mitigate the risk since compromised accounts or insider threats could still pose serious threats. Organizations with extensive IPv6 deployments and active SNMP monitoring systems face the highest exposure, as these environments provide the necessary conditions for exploitation.
Mitigation strategies for this vulnerability require immediate implementation of Cisco's recommended security patches and updates, specifically addressing the CSCvb14640 bug fix. Network administrators should implement strict access controls and credential management policies to minimize the risk of unauthorized access to SNMP management interfaces. The deployment of network segmentation and monitoring solutions can help detect anomalous SNMP polling patterns that might indicate exploitation attempts. Additionally, organizations should consider temporarily disabling IPv6 SNMP support on affected devices until comprehensive security updates are applied. This vulnerability aligns with CWE-129, which addresses improper validation of input boundaries, and maps to ATT&CK technique T1499.004 for network denial of service attacks. Regular vulnerability assessments and security audits should be conducted to identify similar weaknesses in network infrastructure components, particularly those involving protocol implementations that handle complex address structures. The incident underscores the importance of robust input validation in network protocol implementations and highlights the need for continuous security monitoring of management interfaces.