CVE-2021-0238 : Security Advisory and Response
Learn about CVE-2021-0238 affecting Juniper Networks Junos OS MX Series devices. Find out the impact, affected versions, and mitigation steps for this vulnerability.
Executing certain CLI commands on a Juniper Networks Junos OS-based MX Series configured as a Broadband Network Gateway (BNG) may lead to the system running out of disk space, causing potential complications.
Understanding CVE-2021-0238
This vulnerability affects Juniper Networks Junos OS versions on MX Series devices with specific software versions.
What is CVE-2021-0238?
The vulnerability arises when executing certain CLI commands on a Juniper Networks Junos OS-based MX Series configured as a Broadband Network Gateway (BNG), potentially leading to disk space exhaustion.
The Impact of CVE-2021-0238
The vulnerability can cause the system to run out of disk space, potentially resulting in system instability or other complications on affected devices.
Technical Details of CVE-2021-0238
This section outlines the vulnerability description, affected systems and versions, as well as the exploitation mechanism.
Vulnerability Description
The issue occurs when certain CLI commands are repetitively executed, causing excessive disk usage and system space constraints.
Affected Systems and Versions
The vulnerability affects Junos OS versions on MX Series devices, ranging from 17.3R1 to versions prior to 20.4R2, based on the software release.
Exploitation Mechanism
No malicious exploitation of this vulnerability has been identified by Juniper SIRT, indicating a lower risk of immediate exploitation.
Mitigation and Prevention
In response to CVE-2021-0238, Juniper Networks has released updated software versions and provided specific solutions to address the issue.
Immediate Steps to Take
If impacted, users are advised to restart the 'jl2tpd' daemon, which can help recover the system after executing specific commands.
Long-Term Security Practices
To reduce the risk of exploitation, restricting access to the CLI via access lists or firewall filters to trusted networks, hosts, and users is recommended.
Patching and Updates
Juniper Networks recommends updating impacted devices to the latest software releases, including versions 17.4R3-S5, 18.1R3-S13, 18.2R3-S7, and subsequent releases to mitigate the vulnerability.