CVE-2021-31376 Explained : Impact and Mitigation

An Improper Input Validation vulnerability in Packet Forwarding Engine manager (FXPC) process of Juniper Networks Junos OS can lead to a Denial of Service (DoS) attack by sending specific DHCPv6 packets, crashing the FXPC service. This vulnerability affects Junos OS version 18.4R3-S7 to less than 18.4R3-S8 on ACX Series platforms ACX500, ACX1000, ACX1100, ACX2100, ACX2200, ACX4000, ACX5048, ACX5096.

Understanding CVE-2021-31376

This CVE highlights an improper input validation flaw in Juniper Networks Junos OS, impacting certain ACX Series platforms, potentially leading to a DoS attack.

What is CVE-2021-31376?

It is an Improper Input Validation vulnerability in the FXPC process of Juniper Networks Junos OS, allowing attackers to cause a Denial of Service by exploiting specific DHCPv6 packets.

The Impact of CVE-2021-31376

This vulnerability has a CVSS base score of 7.5, rated as High severity, with low attack complexity and a high impact on availability. However, Juniper SIRT has not detected any malicious exploitation yet.

Technical Details of CVE-2021-31376

This section provides insights into the vulnerability, affected systems, and the exploitation mechanism.

Vulnerability Description

The vulnerability allows attackers to trigger a DoS condition by sending crafted DHCPv6 packets to affected devices, leading to the crashing of the FXPC service.

Affected Systems and Versions

Junos OS versions 18.4R3-S7 to less than 18.4R3-S8 on ACX Series platforms including ACX500, ACX1000, ACX1100, ACX2100, ACX2200, ACX4000, ACX5048, ACX5096 are affected by this vulnerability.

Exploitation Mechanism

Attackers can exploit this vulnerability by sending specific DHCPv6 packets to the targeted devices, causing the FXPC service to crash.

Mitigation and Prevention

To protect systems from this vulnerability, immediate steps need to be taken alongside long-term security practices and timely patching.

Immediate Steps to Take

Ensure systems are updated to Junos OS 18.4R3-S8 to mitigate this vulnerability.

Long-Term Security Practices

Implement network segmentation, access controls, and monitor DHCPv6 traffic to detect and prevent potential attacks.

Patching and Updates

Juniper Networks has released Junos OS 18.4R3-S8 as the solution to address this specific issue.