CVE-2021-31379 : Exploit Details and Defense Strategies

An Incorrect Behavior Order vulnerability in the MAP-E automatic tunneling mechanism of Juniper Networks Junos OS allows an attacker to send certain malformed IPv4 or IPv6 packets to cause a Denial of Service (DoS) to the PFE on the device. This issue affects Juniper Networks Junos OS on MX Series with certain MPC cards when MAP-E IP reassembly is enabled on these cards. It has a CVSS base score of 7.5, indicating a HIGH severity.

Understanding CVE-2021-31379

This CVE involves an Incorrect Behavior Order vulnerability in the MAP-E automatic tunneling mechanism, impacting Juniper Networks Junos OS on specific MX Series hardware with MPC cards.

What is CVE-2021-31379?

CVE-2021-31379 is an Incorrect Behavior Order vulnerability in Junos OS that allows an attacker to trigger a Denial of Service condition on affected devices.

The Impact of CVE-2021-31379

The vulnerability allows an attacker to disrupt the PFE on the device by sending malformed IPv4 or IPv6 packets, leading to a sustained Denial of Service (DoS) condition.

Technical Details of CVE-2021-31379

The vulnerability affects Junos OS on MX Series with specific MPC cards when MAP-E IP reassembly is enabled on these cards.

Vulnerability Description

Attackers exploit the MAP-E automatic tunneling mechanism to disrupt device operation by sending malformed IPv4 or IPv6 packets, resulting in a Denial of Service (DoS) condition.

Affected Systems and Versions

Junos OS versions from 17.2 to 19.3 are affected, with certain releases being vulnerable prior to specific patch levels.

Exploitation Mechanism

The vulnerability can be exploited by sending malformed IPv4 or IPv6 packets to trigger the Denial of Service (DoS) condition.

Mitigation and Prevention

To address CVE-2021-31379, Juniper Networks has released specific software updates for affected Junos OS versions. Additionally, workarounds can be implemented to mitigate the risk.

Immediate Steps to Take

Customers should apply the recommended software updates provided by Juniper Networks to address the vulnerability.

Long-Term Security Practices

Implement regular software updates and security patches to protect systems from known vulnerabilities and threats.

Patching and Updates

Ensure that the Junos OS software is regularly updated to the latest versions to mitigate security risks.