CVE-2021-0289

Junos OS: User-defined ARP Policer isn't applied on Aggregated Ethernet (AE) interface until firewall process is restarted

Description

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: __default_arp_policer__ <<< 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.

Remediation

Solution:

  • The following software releases have been updated to resolve this specific issue: For all platforms, except SRX Series, using Junos OS 15.1R7-S10, 18.4R2-S9, 18.4R3-S9, 19.4R3-S4, 20.1R3, 20.2R3-S2, 20.4R3, 21.1R2, 21.2R1, and all subsequent releases. On SRX series using Junos OS 18.4R2-S9, 18.4R3-S9, 19.4R3-S4. 20.1R3, 20.4R3, 21.1R2, 21.2R1, and all subsequent releases.

Workaround:

  • There is no workaround for this issue. If affected by this issue, to recover from its impact, restart the firewall process to update the ARP Policer on the AE interface unit(s). From the CLI issue: cli> restart firewall Note: no side effects on firewall restart shall be seen when issuing this command.

Category

6.5
CVSS
Severity: Medium
CVSS 3.1 •
CVSS 2.0 •
EPSS 0.06%
Vendor Advisory juniper.net
Affected: Juniper Networks Junos OS
Affected: Juniper Networks Junos OS
Affected: Juniper Networks Junos OS Evolved
Published at:
Updated at:

References

Link Tags
https://kb.juniper.net/JSA11191 vendor advisory

Frequently Asked Questions

What is the severity of CVE-2021-0289?
CVE-2021-0289 has been scored as a medium severity vulnerability.
How to fix CVE-2021-0289?
To fix CVE-2021-0289: The following software releases have been updated to resolve this specific issue: For all platforms, except SRX Series, using Junos OS 15.1R7-S10, 18.4R2-S9, 18.4R3-S9, 19.4R3-S4, 20.1R3, 20.2R3-S2, 20.4R3, 21.1R2, 21.2R1, and all subsequent releases. On SRX series using Junos OS 18.4R2-S9, 18.4R3-S9, 19.4R3-S4. 20.1R3, 20.4R3, 21.1R2, 21.2R1, and all subsequent releases.
Is CVE-2021-0289 being actively exploited in the wild?
As for now, there are no information to confirm that CVE-2021-0289 is being actively exploited. According to its EPSS score, there is a ~0% probability that this vulnerability will be exploited by malicious actors in the next 30 days.
What software or system is affected by CVE-2021-0289?
CVE-2021-0289 affects Juniper Networks Junos OS, Juniper Networks Junos OS, Juniper Networks Junos OS Evolved.
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