CVE-2021-0289: Junos OS: User-defined ARP Policer isn't applied on Aggregated Ethernet (AE) interface until firewall process is restarted
When user-defined ARP Policer is configured and applied on one or more Aggregated Ethernet (AE) interface units, a Time-of-check Time-of-use (TOCTOU) Race Condition vulnerability between the Device Control Daemon (DCD) and firewall process (dfwd) daemons of Juniper Networks Junos OS allows an attacker to bypass the user-defined ARP Policer. In this particular case the User ARP policer is replaced with default ARP policer. To review the desired ARP Policers and actual state one can run the command "show interfaces <> extensive" and review the output. See further details below. An example output is: show interfaces extensive | match policer Policer: Input: defaultarppolicer <<< incorrect if user ARP Policer was applied on an AE interface and the default ARP Policer is displayed Policer: Input: jtac-arp-ae5.317-inet-arp <<< correct if user ARP Policer was applied on an AE interface For all platforms, except SRX Series: This issue affects Juniper Networks Junos OS: All versions 5.6R1 and all later versions prior to 18.4 versions prior to 18.4R2-S9, 18.4R3-S9 with the exception of 15.1 versions 15.1R7-S10 and later versions; 19.4 versions prior to 19.4R3-S3; 20.1 versions prior to 20.1R3; 20.2 versions prior to 20.2R3-S2; 20.3 version 20.3R1 and later versions; 20.4 versions prior to 20.4R3; 21.1 versions prior to 21.1R2; This issue does not affect Juniper Networks Junos OS versions prior to 5.6R1. On SRX Series this issue affects Juniper Networks Junos OS: 18.4 versions prior to 18.4R2-S9, 18.4R3-S9; 19.4 versions prior to 19.4R3-S4; 20.1 versions prior to 20.1R3; 20.2 versions prior to 20.2R3-S2; 20.3 version 20.3R1 and later versions; 20.4 versions prior to 20.4R3; 21.1 versions prior to 21.1R2. This issue does not affect 18.4 versions prior to 18.4R1 on SRX Series. This issue does not affect Junos OS Evolved.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
Juniper Networks Junos OSto a version that resolves this vulnerability.Fixed in 20.1R3 - Upgrade
Upgrade
Juniper Networks Junos OSto a version that resolves this vulnerability.Fixed in 20.4R3 - Upgrade
Upgrade
Juniper Networks Junos OSto a version that resolves this vulnerability.Fixed in 21.1R2 - Upgrade
Upgrade
Juniper Networks Junos OSto a version that resolves this vulnerability.Fixed in 21.2R1 - Upgrade
Upgrade
Juniper Networks Junos OSto a version that resolves this vulnerability.Fixed in 20.2R3-S2 - Upgrade
Upgrade
Juniper Networks Junos OSto a version that resolves this vulnerability.Fixed in 18.4R2-S9 - Upgrade
Upgrade
Juniper Networks Junos OSto a version that resolves this vulnerability.Fixed in 18.4R3-S9 - Upgrade
Upgrade
Juniper Networks Junos OSto a version that resolves this vulnerability.Fixed in 19.4R3-S4 - Upgrade
Upgrade
Juniper Networks Junos OSto a version that resolves this vulnerability.Fixed in 20.3R1 - Upgrade
Upgrade
Juniper Networks Junos OSto a version that resolves this vulnerability.Fixed in 15.1R7-S10 - Operational
Verify the desired and actual ARP policers by running: show interfaces <interface> extensive, and review the output for the Policer: Input (compare expected user-defined ARP policer vs displayed Policer). In the AE case, user-defined ARP policer may be shown incorrectly as the default ARP policer until restart; for AE, confirm that the correct user ARP policer is in effect.
- Operational
On SRX Series, when using Junos OS 18.4 versions prior to 18.4R2-S9, 18.4R3-S9, 19.4 versions prior to 19.4R3-S4, 20.1 versions prior to 20.1R3, 20.2 versions prior to 20.2R3-S2, 20.4 versions prior to 20.4R3, or 21.1 versions prior to 21.1R2, the user-defined ARP policer is not applied on Aggregated Ethernet (AE) interface units until the firewall process is restarted. Restart the firewall process to ensure the user-defined ARP policer is applied on AE interfaces.
Event History
Frequently Asked Questions
What is the severity of CVE-2021-0289?
The severity of CVE-2021-0289 is classified as medium, indicating a moderately serious vulnerability.
How do I fix CVE-2021-0289?
To fix CVE-2021-0289, it is recommended to apply the latest patches provided by Juniper Networks for affected versions of Junos OS.
Which versions of Junos OS are affected by CVE-2021-0289?
CVE-2021-0289 affects Junos OS versions between 5.7 and 15.1, as well as 15.2 to 18.4, and various 20.x versions.
Does CVE-2021-0289 affect all Juniper devices?
No, CVE-2021-0289 specifically affects devices where user-defined ARP Policer is configured on Aggregated Ethernet interface units.
What are the implications of CVE-2021-0289?
The implications of CVE-2021-0289 include potential denial of service or unauthorized access to network resources due to the race condition vulnerability.