CVE-2021-0223 : Security Advisory and Response

A local privilege escalation vulnerability in telnetd.real of Juniper Networks Junos OS allows a locally authenticated user to execute commands as root, affecting versions prior to 20.2R2.

Understanding CVE-2021-0223

This CVE refers to a local privilege escalation vulnerability in Juniper Networks Junos OS that could allow an authenticated shell user to gain root privileges by exploiting the telnetd.real binary.

What is CVE-2021-0223?

The vulnerability in telnetd.real of Juniper Networks Junos OS enables a locally authenticated user to escalate privileges and execute arbitrary commands as root. This could lead to unauthorized access and control over the system.

The Impact of CVE-2021-0223

The impact of this vulnerability is rated as HIGH, with a base score of 7.8 according to the CVSS v3.1 metrics. It poses a significant threat to the confidentiality, integrity, and availability of affected systems.

Technical Details of CVE-2021-0223

This section provides more technical insights into the vulnerability.

Vulnerability Description

The vulnerability arises from the setuid permissions enabled for telnetd.real, allowing local users to run it with root privileges, leading to unauthorized command execution.

Affected Systems and Versions

Juniper Networks Junos OS versions prior to 20.2R2 are affected by this privilege escalation vulnerability.

Exploitation Mechanism

The vulnerability can be exploited by a locally authenticated user leveraging the setuid permissions on the telnetd.real binary.

Mitigation and Prevention

To safeguard systems from CVE-2021-0223, immediate and long-term security measures are crucial.

Immediate Steps to Take

Implement access lists or firewall filters to restrict CLI access to trusted administrative networks. Limit access to the Junos OS shell to authorized system administrators.

Long-Term Security Practices

Regularly apply software updates and patches from Juniper Networks to eliminate vulnerabilities and enhance system security.

Patching and Updates

Update to the recommended software releases resolved by Juniper Networks to address this specific vulnerability, ensuring ongoing protection against potential exploits.