CVE-2017-6775 in StarOS
Summary
by MITRE
A vulnerability in the CLI of Cisco ASR 5000 Series Aggregated Services Routers running the Cisco StarOS operating system could allow an authenticated, local attacker to elevate their privileges to admin-level privileges. The vulnerability is due to incorrect permissions that are given to a set of users. An attacker could exploit this vulnerability by logging in to the shell of an affected device and elevating their privileges by modifying environment variables. An exploit could allow the attacker to gain admin-level privileges and take control of the affected device. Cisco Bug IDs: CSCvd47741. Known Affected Releases: 21.0.v0.65839.
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Analysis
by VulDB Data Team • 01/09/2021
The vulnerability identified as CVE-2017-6775 represents a critical privilege escalation flaw within the Cisco ASR 5000 Series Aggregated Services Routers operating on the Cisco StarOS platform. This issue specifically targets the Command Line Interface implementation where improper access controls have been configured for certain user groups. The flaw manifests as a misconfiguration in the permission model that allows authenticated local users to manipulate their privileges through deliberate modification of environmental variables. The vulnerability affects the 21.0.v0.65839 release version and is documented under Cisco Bug ID CSCvd47741, highlighting the severity of the misconfigured access controls that persist within the system's authorization framework.
The technical exploitation of this vulnerability involves a sophisticated approach that leverages the inherent design flaw in the CLI's permission handling mechanisms. An authenticated attacker who gains shell access to the affected device can manipulate environment variables to bypass normal privilege boundaries and escalate their access level to administrative privileges. This type of attack falls under the category of privilege escalation attacks where the attacker exploits improper access controls to gain unauthorized administrative rights. The vulnerability demonstrates a clear violation of the principle of least privilege, where users are granted more access than necessary for their legitimate operations. The flaw directly relates to CWE-276, which addresses improper permissions for a resource, and can be mapped to ATT&CK technique T1068, which covers exploit for privilege escalation through local system access.
The operational impact of this vulnerability extends beyond simple unauthorized access, as it provides attackers with complete administrative control over the affected routers. Once an attacker achieves admin-level privileges, they can modify routing configurations, access sensitive network data, disable security features, and potentially disrupt network services across the entire infrastructure. The affected Cisco ASR 5000 Series routers serve as critical aggregation points in many network architectures, making this vulnerability particularly dangerous for organizations relying on these devices for core network operations. The local nature of the attack means that the attacker must first gain legitimate access to the device, but once achieved, the privilege escalation capability provides unrestricted access to the entire router management interface. This vulnerability directly threatens the integrity and availability of network services, as an attacker could potentially modify routing tables, create backdoors, or disable security mechanisms that protect the network from external threats.
Organizations should immediately implement mitigations that focus on strengthening access controls and monitoring for unauthorized privilege escalation attempts. The recommended approach includes applying the latest security patches provided by Cisco, implementing strict access control policies that limit shell access to only essential personnel, and establishing comprehensive monitoring for environment variable modifications. Network segmentation and multi-factor authentication for administrative access should be implemented to reduce the attack surface. Additionally, regular security audits should verify that proper permissions are configured for all user accounts and that no unauthorized access paths exist within the system. The vulnerability highlights the importance of maintaining proper access control mechanisms and demonstrates that even authenticated users can pose significant risks if their privileges are not properly constrained. Organizations must also consider implementing network monitoring solutions that can detect anomalous behavior patterns associated with privilege escalation attempts and ensure that administrative access is logged and audited for security compliance purposes.