CVE-2021-0273 : Security Advisory and Response

Juniper Networks Junos OS on ACX5800, EX9200 Series, MX10000 Series, MX240, MX480, MX960 has a vulnerability, allowing an attacker to cause a Denial of Service (DoS) condition. Find out the impact, affected systems, exploitation mechanism, and mitigation steps below.

Understanding CVE-2021-0273

This CVE affects Junos OS and Junos OS Evolved on various Juniper Networks devices with Trio line cards, potentially leading to a Denial of Service (DoS) due to an incorrect control flow implementation.

What is CVE-2021-0273?

An always-incorrect control flow implementation in Juniper Networks Junos OS and Junos OS Evolved on specific devices allows an attacker to exploit a vulnerability in the PFE UCODE microcode of the Trio chipset, causing a potential DoS condition by looping the packet with an unreachable exit condition.

The Impact of CVE-2021-0273

The vulnerability affects specific line cards with LT-LT interfaces, potentially leading to sustained DoS conditions when exploited. It impacts Juniper Networks Junos OS and Junos OS Evolved on certain devices.

Technical Details of CVE-2021-0273

The vulnerability involves an incorrect control flow implementation, impacting the Trio chipset on affected line cards. Exploitation can cause packets to loop and create a DoS condition on the device interfaces.

Vulnerability Description

The vulnerability in Junos OS and Junos OS Evolved may allow an attacker to create a sustained DoS condition by looping packets on specific LT-LT interfaces.

Affected Systems and Versions

Juniper Networks Junos OS on ACX5800, EX9200 Series, MX10000 Series, MX240, MX480, MX960 are affected. Versions from 15.1F6 to 19.4 are vulnerable, excluding specific releases.

Exploitation Mechanism

Exploiting an interdependency in the Trio chipset with various line cards, an attacker can cause packets to loop, leading to DoS via LT-LT interfaces.

Mitigation and Prevention

To address CVE-2021-0273, follow these steps:

Immediate Steps to Take

Monitor LT-LT interfaces for excessive traffic. Apply relevant patches for Junos OS and Junos OS Evolved releases.

Long-Term Security Practices

Regularly update networking devices, implement best security practices, and monitor for unusual traffic patterns to detect potential exploitation.

Patching and Updates

Ensure the affected Junos OS and Junos OS Evolved releases are updated to the fixed versions provided by Juniper Networks.