CVE-2021-0205 : What You Need to Know
Discover the impact of CVE-2021-0205 vulnerability in Juniper Networks MX Series devices running Junos OS versions 17.3 to 20.2. Learn about the technical details, mitigation steps, and solutions.
When the "Intrusion Detection Service" (IDS) feature is configured on Juniper Networks MX series with a dynamic firewall filter using IPv6 source or destination prefix, it may incorrectly match the prefix as /32, causing the filter to block unexpected traffic. This issue affects only IPv6 prefixes when used as source and destination. Learn more about the impact, technical details, mitigation steps, and solutions related to this vulnerability.
Understanding CVE-2021-0205
This section provides detailed insights into the CVE-2021-0205 vulnerability affecting Juniper Networks' Junos OS on MX Series devices.
What is CVE-2021-0205?
CVE-2021-0205 is a vulnerability in Juniper Networks MX Series devices when the IDS feature with a dynamic firewall filter is configured using IPv6 source or destination prefixes. This may lead to incorrect matching of the prefix as /32, resulting in the unintended blocking of traffic.
The Impact of CVE-2021-0205
The vulnerability impacts Juniper Networks Junos OS versions 17.3 to 20.2 on MX Series devices with MS-MPC, MS-MIC, or MS-SPC3 service cards when the IDS service is enabled for IPv6 prefixes.
Technical Details of CVE-2021-0205
In this section, we delve into the technical aspects of the CVE-2021-0205 vulnerability.
Vulnerability Description
The vulnerability arises due to the IDS feature incorrectly matching IPv6 prefixes as /32, leading to unexpected traffic blocking.
Affected Systems and Versions
Juniper Networks MX Series devices are affected by this vulnerability across various Junos OS versions ranging from 17.3 to 20.2.
Exploitation Mechanism
There is no known malicious exploitation of this vulnerability reported by Juniper SIRT.
Mitigation and Prevention
To address and prevent the CVE-2021-0205 vulnerability, consider the following steps.
Immediate Steps to Take
Disable the IDS configuration to mitigate the impact of the vulnerability.
Long-Term Security Practices
Regularly update and patch Juniper Junos OS on MX Series devices to the latest software releases that address this specific issue.
Patching and Updates
Update Junos OS to versions like 17.3R3-S10, 17.4R3-S3, 18.1R3-S11, 18.2R3-S6, 18.3R3-S4, 18.4R3-S6, 19.1R2-S2, 19.1R3-S3, 19.2R3-S1, 19.3R2-S5, 19.3R3-S1, 19.4R3, 20.1R2, 20.2R2, 20.3R1, or any subsequent releases.