In a significant security disclosure, researchers at Embedi have identified a critical vulnerability in Cisco’s IOS and IOS XE Software, which poses a pronounced threat to network devices. This flaw could enable an unauthenticated remote attacker to execute arbitrary code, thereby seizing complete control of vulnerable systems and intercepting sensitive network traffic.
The specific vulnerability, classified as a stack-based buffer overflow (CVE-2018-0171), emerges from inadequate validation of packet data within the Smart Install Client—a feature designed to ease the deployment of network switches by automating configuration and image management processes. With Cisco’s recent patch addressing this issue, it has been assigned a high risk rating with a Common Vulnerability Scoring System (CVSS) score of 9.8, indicating it is critical in severity.
Embedi’s research denotes that over 8.5 million devices are exposed on the internet, with nearly 250,000 remaining unpatched. For attackers, exploitation involves sending specifically crafted Smart Install messages to affected devices on TCP port 4786, which is enabled by default in many configurations.
Cisco’s advisory elaborates on the exact mechanism of the buffer overflow, stating that the vulnerability arises in the function responsible for processing discovery messages, where the size of copied data is not properly validated. Consequently, an attacker can control both the size and data directly from network packets. This flaw does not only facilitate remote code execution but can also induce a denial-of-service state by causing the affected devices to enter an infinite loop.
Demonstrations of this vulnerability were showcased at a conference in Hong Kong, following its initial report to Cisco in May 2017. Researchers exhibited attacks that allowed them to reset passwords on a Cisco Catalyst 2960 switch and capture traffic between the switch and connected devices.
The range of potentially affected hardware encompasses several models from Cisco’s Catalyst series, including the 4500, 3850, 2960, and 3650, among others. Cisco has remediated the vulnerabilities in these devices with its recent patches released on March 28, 2018.
Business owners should prioritize applying these patches to mitigate risks associated with exploitation of this critical vulnerability. Ensuring that all affected network equipment is updated promptly could significantly reduce the risk of unauthorized access and potential data breaches.
In terms of attacker tactics, the initial access could be achieved through exploitation of the buffer overflow, while persistence and privilege escalation might follow once the attacker gains control over the device. The MITRE ATT&CK framework highlights several techniques relevant to this exploitation, underlying the importance of awareness and swift remediation in the cybersecurity landscape.