CVE-2020-3218 in IOS XE
Summary
by MITRE
A vulnerability in the web UI of Cisco IOS XE Software could allow an authenticated, remote attacker with administrative privileges to execute arbitrary code with root privileges on the underlying Linux shell. The vulnerability is due to improper validation of user-supplied input. An attacker could exploit this vulnerability by first creating a malicious file on the affected device itself and then uploading a second malicious file to the device. A successful exploit could allow the attacker to execute arbitrary code with root privileges or bypass licensing requirements on the device.
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Analysis
by VulDB Data Team • 10/21/2020
The vulnerability identified as CVE-2020-3218 represents a critical security flaw within Cisco IOS XE Software's web user interface that enables authenticated remote code execution with elevated privileges. This weakness stems from inadequate input validation mechanisms that fail to properly sanitize user-supplied data, creating an exploitable path for malicious actors who possess administrative credentials. The vulnerability specifically targets the underlying Linux shell of affected devices, allowing successful exploitation to result in complete system compromise with root-level access. The flaw operates through a two-stage attack methodology where an attacker must first establish a malicious file on the target device before uploading a secondary malicious component, demonstrating the complexity and sophistication required to achieve successful exploitation.
From a technical perspective, this vulnerability falls under the CWE-20 category of "Improper Input Validation" and aligns with ATT&CK technique T1059.004 for command and scripting interpreter. The vulnerability's exploitation requires an attacker to have administrative privileges, which significantly reduces the attack surface compared to unauthenticated exploits, but the privilege escalation aspect remains particularly dangerous. The improper validation allows malicious input to be processed through the web interface and subsequently executed within the Linux environment, bypassing normal security controls and access restrictions. This cross-platform execution path from web interface to Linux shell represents a significant architectural weakness in the software's security model.
The operational impact of CVE-2020-3218 extends beyond simple code execution to include complete system compromise and potential licensing bypass capabilities. An attacker with administrative access could leverage this vulnerability to establish persistent backdoors, exfiltrate sensitive data, or disrupt network operations through arbitrary command execution. The ability to bypass licensing requirements adds another dimension to the threat, potentially allowing unauthorized use of premium features or services. Organizations running affected Cisco IOS XE software versions face significant risk of unauthorized access to their network infrastructure, particularly in environments where administrative credentials might be compromised or where the web interface is accessible from untrusted networks.
Mitigation strategies for this vulnerability should prioritize immediate patching of affected devices with Cisco's security updates, which address the input validation flaws in the web UI component. Network segmentation and access control measures should be implemented to restrict access to the web interface, ensuring that only authorized administrative personnel can reach the vulnerable interface. Additional defensive measures include monitoring for unusual file creation patterns and unauthorized file uploads that might indicate exploitation attempts. Organizations should also implement robust credential management practices, including regular credential rotation and multi-factor authentication for administrative access. The vulnerability demonstrates the importance of input validation in web applications and highlights the need for comprehensive security testing of administrative interfaces to prevent similar privilege escalation scenarios.