CVE-2021-0271 Explained : Impact and Mitigation

A Double Free vulnerability in Juniper Networks Junos OS could allow an adjacent attacker to trigger a Denial of Service (DoS) by exploiting the software forwarding interface daemon (sfid) process. This vulnerability affects various EX Series devices on specific versions of Junos OS, creating a sustained DoS condition. Juniper SIRT has not observed any malicious exploitation of this vulnerability.

Understanding CVE-2021-0271

This CVE highlights a Double Free vulnerability that impacts certain versions of Juniper Networks Junos OS, leading to a DoS risk when an adjacent attacker sends a crafted ARP packet to the device.

What is CVE-2021-0271?

The CVE-2021-0271 vulnerability in Juniper Networks Junos OS enables an adjacently-connected attacker to execute a DoS attack by manipulating the sfid process with a carefully crafted ARP packet. This can result in a sustained DoS state on the affected devices.

The Impact of CVE-2021-0271

The vulnerability poses a medium severity risk with a CVSS base score of 6.5. Although it does not impact confidentiality or integrity, the availability of the affected systems can be significantly affected. It affects specific Marvell-chipset based EX Series devices running certain Junos OS versions.

Technical Details of CVE-2021-0271

This section outlines the technical aspects of the CVE, including vulnerability description, affected systems, and exploitation mechanism.

Vulnerability Description

The vulnerability arises due to a Double Free issue in the sfid process of Juniper Networks Junos OS, triggered by a crafted ARP packet from an adjacent attacker, leading to a sustained DoS condition.

Affected Systems and Versions

Juniper Networks Junos OS versions 12.3 prior to 12.3R12-S17 and version 15.1 prior to 15.1R7-S8 on specific EX Series devices are affected by this vulnerability.

Exploitation Mechanism

An adjacent attacker can exploit the vulnerability by sending a specifically crafted ARP packet to the device, causing the sfid process to malfunction and result in a DoS condition.

Mitigation and Prevention

To address CVE-2021-0271, immediate steps, security best practices, and the importance of timely patching are crucial.

Immediate Steps to Take

Ensure the affected Junos OS versions are updated to the patched releases: 12.3R12-S17, 15.1R7-S8, or later. Monitor network traffic for any signs of ARP packet manipulation.

Long-Term Security Practices

Implement network segmentation, access control policies, and regular security audits to detect and mitigate potential risks effectively.

Patching and Updates

Regularly check for security advisories from Juniper Networks and apply patches promptly to safeguard against known vulnerabilities.