CVE-2017-3819 : Exploit Details and Defense Strategies

A privilege escalation vulnerability in the Secure Shell (SSH) subsystem of Cisco StarOS operating system could allow remote attackers to gain root shell access.

Understanding CVE-2017-3819

This CVE identifies a privilege escalation vulnerability in the SSH subsystem of Cisco StarOS, affecting various Cisco ASR and Virtualized Packet Core devices.

What is CVE-2017-3819?

The vulnerability allows authenticated remote attackers to exploit SSH or SFTP login processes, potentially leading to unrestricted root shell access.

The Impact of CVE-2017-3819

Attackers with authenticated access can gain root privileges on affected routers by providing malicious input during SSH or SFTP login.
The vulnerability affects Cisco ASR 5000/5500/5700 Series devices and Virtualized Packet Core devices running specific StarOS versions.

Technical Details of CVE-2017-3819

This section provides detailed technical insights into the vulnerability.

Vulnerability Description

Lack of input validation during SSH or SFTP login in Cisco StarOS leads to privilege escalation.

Affected Systems and Versions

Cisco ASR 5000/5500/5700 Series devices running StarOS versions after 17.7.0 and before 18.7.4, 19.5, and 20.2.3 with SSH configurations are vulnerable.
Cisco Virtualized Packet Core devices running StarOS prior to N4.2.7 (19.3.v7) and N4.7 (20.2.v0) with SSH configurations are also affected.

Exploitation Mechanism

Attackers exploit the vulnerability by supplying crafted user input during SSH or SFTP login, requiring valid credentials and TCP connection to port 22.

Mitigation and Prevention

Steps to address and prevent exploitation of CVE-2017-3819.

Immediate Steps to Take

Apply patches provided by Cisco to fix the vulnerability.
Restrict network access to SSH services to limit exposure.
Monitor network traffic for signs of exploitation.

Long-Term Security Practices

Regularly update and patch systems to prevent known vulnerabilities.
Implement strong password policies and multi-factor authentication.

Patching and Updates

Cisco has released patches to address the vulnerability. Ensure timely installation of these patches to secure the affected systems.