CVE-2017-3850 in IOS
Summary
by MITRE
A vulnerability in the Autonomic Networking Infrastructure (ANI) feature of Cisco IOS Software (15.4 through 15.6) and Cisco IOS XE Software (3.7 through 3.18, and 16) could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition. The vulnerability is due to incomplete input validation on certain crafted packets. An attacker could exploit this vulnerability by sending a crafted IPv6 packet to a device that is running a Cisco IOS Software or Cisco IOS XE Software release that supports the ANI feature. A device must meet two conditions to be affected by this vulnerability: (1) the device must be running a version of Cisco IOS Software or Cisco IOS XE Software that supports ANI (regardless of whether ANI is configured); and (2) the device must have a reachable IPv6 interface. An exploit could allow the attacker to cause the affected device to reload. Cisco Bug IDs: CSCvc42729.
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Analysis
by VulDB Data Team • 08/28/2024
The vulnerability identified as CVE-2017-3850 resides within the Autonomic Networking Infrastructure feature of Cisco IOS and IOS XE software versions ranging from 15.4 through 15.6 and 3.7 through 3.18, as well as 16. This flaw represents a critical security weakness that enables unauthenticated remote attackers to execute denial of service attacks against affected network devices. The vulnerability specifically stems from incomplete input validation mechanisms that fail to properly scrutinize incoming IPv6 packets destined for devices implementing the ANI framework. The flaw manifests when the system processes malformed or specially crafted IPv6 packets that exploit gaps in the validation logic, ultimately leading to system instability and potential device reloads.
The technical implementation of this vulnerability operates through a specific attack vector involving IPv6 packet manipulation that targets the ANI processing modules within Cisco networking equipment. When an attacker sends specifically crafted IPv6 packets to a vulnerable device, the incomplete input validation allows malicious data to bypass normal processing checks and potentially trigger memory corruption or resource exhaustion within the ANI subsystem. This condition creates a scenario where the device's normal operational flow becomes disrupted, ultimately resulting in a system reload that effectively denies service to legitimate network users. The vulnerability's exploitation requires minimal privileges since no authentication is necessary, making it particularly dangerous for network infrastructure components that are accessible from external networks.
The operational impact of CVE-2017-3850 extends beyond simple service disruption to potentially compromise network availability and reliability across affected deployments. Network administrators face significant challenges in mitigating this vulnerability since the attack can originate from any external IPv6 address that can reach the target device, making it difficult to implement effective network segmentation strategies. The requirement for only two conditions to exploit the vulnerability - having ANI supported software regardless of configuration and a reachable IPv6 interface - means that many network devices could be at risk without active configuration awareness. This characteristic aligns with CWE-20, which identifies improper input validation as a fundamental weakness that can lead to various security issues including denial of service conditions.
Organizations affected by this vulnerability must consider the broader implications for their network infrastructure security posture, particularly as the attack can occur without any authentication requirements and potentially affect critical network operations. The vulnerability's potential to cause device reloads creates cascading effects that can impact network availability, especially in environments where network devices are not regularly monitored for such conditions. Mitigation strategies should include immediate software updates to patched versions, network segmentation to limit IPv6 access to only necessary devices, and monitoring for suspicious IPv6 traffic patterns that may indicate exploitation attempts. The ATT&CK framework's T1499.004 technique for network denial of service through resource exhaustion aligns with this vulnerability's exploitation methods, emphasizing the importance of proper input validation and network access controls.
Cisco's identification of this issue through Bug ID CSCvc42729 highlights the company's recognition of the severity of incomplete input validation flaws in network infrastructure software. The vulnerability demonstrates how seemingly isolated processing modules within complex network operating systems can become attack vectors when proper validation mechanisms are absent. Security practitioners should understand that this vulnerability represents a classic example of how insufficient validation can lead to complete system compromise, particularly in network infrastructure where availability is paramount. The remediation approach requires careful consideration of network architecture changes and software update strategies that may impact network operations during the patching process, making proper planning and testing essential for effective vulnerability management.