CVE-2017-6774 in StarOS
Summary
by MITRE
A vulnerability in Cisco ASR 5000 Series Aggregated Services Routers running the Cisco StarOS operating system could allow an authenticated, remote attacker to overwrite or modify sensitive system files. The vulnerability is due to the inclusion of sensitive system files within specific FTP subdirectories. An attacker could exploit this vulnerability by overwriting sensitive configuration files through FTP. An exploit could allow the attacker to overwrite configuration files on an affected system. Cisco Bug IDs: CSCvd47739. Known Affected Releases: 21.0.v0.65839.
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Analysis
by VulDB Data Team • 01/09/2021
The vulnerability identified as CVE-2017-6774 affects Cisco ASR 5000 Series Aggregated Services Routers operating with the Cisco StarOS system software, representing a critical security flaw that enables authenticated remote attackers to compromise system integrity through file manipulation. This vulnerability specifically targets the configuration and operational files that are accessible through the File Transfer Protocol implementation within the router's file system structure, creating a significant attack surface that could lead to system compromise and unauthorized access to sensitive network infrastructure. The flaw exists in the way sensitive system files are organized within specific FTP subdirectories, making them potentially writable by authenticated users who should not possess such privileges.
The technical exploitation of this vulnerability occurs through the FTP protocol implementation within the StarOS operating system, where an authenticated attacker can leverage the improperly configured file permissions to overwrite or modify critical system configuration files. This represents a classic privilege escalation vulnerability that allows an attacker to manipulate system files that should remain protected from unauthorized modification, effectively creating a backdoor for persistent access and potential further compromise of the network infrastructure. The vulnerability stems from inadequate access control mechanisms within the FTP subsystem, where sensitive files are not properly protected from modification by authenticated users, directly violating security principles of least privilege and proper file system permissions. According to CWE classification, this vulnerability aligns with CWE-276: Incorrect Permission Assignment for Critical Resources, which addresses improper access control mechanisms that allow unauthorized modification of system-critical files.
The operational impact of this vulnerability extends beyond simple file modification, as it provides attackers with the capability to alter critical router configuration parameters that govern network traffic handling, security policies, and system behavior. An attacker who successfully exploits this vulnerability could potentially redirect network traffic, disable security features, modify routing tables, or establish persistent access points within the network infrastructure. The affected Cisco ASR 5000 Series routers serve as critical network aggregation points, making this vulnerability particularly dangerous as it could enable attackers to compromise large segments of network traffic flow and potentially disrupt services across multiple network domains. The specific affected release version 21.0.v0.65839 indicates that this vulnerability existed in a particular software release cycle, highlighting the importance of timely patch management and software version monitoring for network infrastructure components.
Mitigation strategies for CVE-2017-6774 should prioritize immediate implementation of network segmentation and access control measures to limit FTP access to only authorized personnel with legitimate administrative requirements. Network administrators should implement strict file permission controls and audit procedures to monitor access to critical system files, ensuring that only designated administrators can modify sensitive configurations. The recommended approach includes disabling unnecessary FTP services where possible, implementing strong authentication mechanisms, and regularly reviewing access logs for suspicious activity patterns. Additionally, organizations should consider implementing network monitoring solutions that can detect anomalous file modification patterns and provide alerts when unauthorized changes occur to critical system files. According to ATT&CK framework, this vulnerability maps to T1078: Valid Accounts and T1490: Inhibit System Recovery, as it allows for persistence through configuration file manipulation and can potentially disrupt system recovery processes. The vulnerability also aligns with T1566: Phishing and T1555: Credentials from Password Stores, as attackers may use compromised credentials to access the FTP subsystem and exploit this flaw for further network infiltration. Regular security assessments and vulnerability scanning should be implemented to identify similar permission misconfigurations across the network infrastructure, particularly in critical network devices that may be vulnerable to similar file system access control flaws.