CVE-2017-6795 in IOS XE
Summary
by MITRE
A vulnerability in the USB-modem code of Cisco IOS XE Software running on Cisco ASR 920 Series Aggregation Services Routers could allow an authenticated, local attacker to overwrite arbitrary files on the underlying operating system of an affected device. The vulnerability is due to improper input validation of the platform usb modem command in the CLI of the affected software. An attacker could exploit this vulnerability by modifying the platform usb modem command in the CLI of an affected device. A successful exploit could allow the attacker to overwrite arbitrary files on the underlying operating system of an affected device. Cisco Bug IDs: CSCvf10783.
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Analysis
by VulDB Data Team • 01/11/2021
The vulnerability identified as CVE-2017-6795 represents a critical file overwrite flaw within the Cisco IOS XE Software running on ASR 920 Series Aggregation Services Routers. This issue stems from inadequate input validation mechanisms within the command line interface implementation, specifically targeting the platform usb modem command functionality. The vulnerability architecture demonstrates a classic improper input validation weakness that allows malicious manipulation of system operations through CLI commands. The affected device architecture processes USB modem commands without sufficient sanitization of user-supplied parameters, creating an attack surface where authenticated local users can manipulate underlying system file structures.
The technical exploitation of this vulnerability occurs through manipulation of the platform usb modem command within the router's command line interface. When an authenticated attacker submits crafted input to this command, the system fails to validate the parameters properly, allowing arbitrary file overwrite operations to be executed against the underlying operating system. This flaw operates at the privilege level of the authenticated user, requiring local access but not elevated privileges, making it particularly concerning for environments where physical or administrative access might be compromised. The vulnerability specifically affects the CLI processing layer of IOS XE software, where command parsing and parameter validation mechanisms are insufficient to prevent malicious file manipulation attempts.
The operational impact of this vulnerability extends beyond simple file overwrite capabilities, as it provides an authenticated attacker with the ability to modify critical system files and potentially compromise the integrity of the entire router operating environment. This vulnerability could enable attackers to replace system binaries, modify configuration files, or manipulate core operating system components that maintain the router's functionality and security posture. The attack vector requires local authentication, which means that unauthorized access to the router's CLI interface is necessary, but once achieved, the attacker can leverage this weakness to establish persistent access or degrade system functionality. The vulnerability affects the fundamental security model of the device, as it allows a local authenticated user to bypass normal file system protections.
Mitigation strategies for CVE-2017-6795 should focus on implementing strict input validation controls within the CLI processing framework of affected Cisco devices. Network administrators should ensure that all affected routers are updated with the latest security patches provided by Cisco, specifically addressing the CSCvf10783 bug fix. Access controls should be strengthened through the implementation of least privilege principles, limiting local administrative access to only authorized personnel. The vulnerability aligns with CWE-20, which describes improper input validation, and represents a significant concern for the ATT&CK framework's privilege escalation and persistence tactics. Organizations should conduct thorough vulnerability assessments to identify all affected devices and implement network segmentation to limit the potential impact of exploitation. Regular security audits of CLI access and command processing should be performed to detect anomalous behavior that might indicate exploitation attempts.