CVE-2020-1649 : Exploit Details and Defense Strategies

In July 2020, Juniper Networks identified a vulnerability in Junos OS impacting the MX Series routers, which could result in a Denial of Service (DoS) attack.

Understanding CVE-2020-1649

This CVE pertains to a specific issue with Junos OS on MX Series devices that leads to the Packet Forwarding Engine (PFE) becoming disabled due to small fragments requiring reassembly.

What is CVE-2020-1649?

The vulnerability in Juniper Networks Junos OS on MX Series routers can be exploited by sending fragmented packets that the system cannot reassemble, resulting in a sustained DoS attack.

The Impact of CVE-2020-1649

The exploitation of this vulnerability could cause a sustained Denial of Service by repeatedly disabling the PFE on affected devices.

Technical Details of CVE-2020-1649

This section covers a detailed overview of the vulnerability.

Vulnerability Description

When Junos OS with specific line cards and inline IP reassembly configurations receives small unprocessable fragments, the PFE is disabled, leading to a potential DoS incident.

Affected Systems and Versions

The vulnerability affects various versions of Junos OS on MX Series routers, ranging from 17.2 to 19.3.

Exploitation Mechanism

Attackers can exploit the vulnerability by continuously sending fragmented packets that trigger the PFE disabling mechanism, causing a DoS.

Mitigation and Prevention

Proactive steps to address and prevent the exploitation of CVE-2020-1649.

Immediate Steps to Take

Update to the patched software releases provided by Juniper Networks.
Regularly monitor network traffic for any suspicious activities.

Long-Term Security Practices

Implement network segmentation to contain potential attacks.
Conduct regular security audits and assessments to identify vulnerabilities.

Patching and Updates

Install the following software updates to mitigate the CVE-2020-1649 issue: Junos OS 17.2R3-S4, 17.3R3-S8, 17.4R2-S9, 17.4R3-S1, 18.1R3-S10, 18.2R2-S6, 18.2R3-S3, 18.2X75-D34, 18.2X75-D41, 18.2X75-D53, 18.2X75-D65, 18.2X75-D430, 18.3R1-S7, 18.3R2-S4, 18.3R3-S2, 18.4R1-S6, 18.4R2-S4, 18.4R3, 19.1R1-S4, 19.1R2-S1, 19.1R3, 19.2R1-S3, 19.2R2, 19.3R2-S2, 19.3R3, 19.4R1, 19.4R2, 20.1R1, and subsequent releases.