CVE-2021-0221: In an EVPN/VXLAN scenario, if an IRB interface with a virtual gateway address (VGA) is configured on a PE, a traffic loop may occur upon receipt of sp...

Description

In an EVPN/VXLAN scenario, if an IRB interface with a virtual gateway address (VGA) is configured on a PE, a traffic loop may occur upon receipt of specific IP multicast traffic. The traffic loop will cause interface traffic to increase abnormally, ultimately leading to a Denial of Service (DoS) in packet processing. The following command could be used to monitor the interface traffic: user@junos> monitor interface traffic Interface Link Input packets (pps) Output packets (pps) et-0/0/1 Up 6492089274364 (70994959) 6492089235319 (70994956) et-0/0/25 Up 343458103 (1) 156844 (0) ae0 Up 9132519197257 (70994959) 9132519139454 (70994956) This issue affects Juniper Networks Junos OS on QFX Series: all versions prior to 17.3R3-S10; 17.4 versions prior to 17.4R2-S12, 17.4R3-S3; 18.1 versions prior to 18.1R3-S11; 18.2 versions prior to 18.2R3-S6; 18.3 versions prior to 18.3R3-S4; 18.4 versions prior to 18.4R2-S5, 18.4R3-S5; 19.1 versions prior to 19.1R1-S6, 19.1R2-S2, 19.1R3-S3; 19.2 versions prior to 19.2R1-S5, 19.2R3-S1; 19.3 versions prior to 19.3R2-S5, 19.3R3; 19.4 versions prior to 19.4R2-S2, 19.4R3; 20.1 versions prior to 20.1R2; 20.2 versions prior to 20.2R1-S2, 20.2R2.

Metrics

CVSS 3.1

6.5/10

CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

EPSS Probability

0.51%

39.4th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

Affected Software

Vendor	Product	Versions	Update
Juniper	Junos	17.3	—
Juniper	Junos	17.4	—
Juniper	Junos	18.1	—
Juniper	Junos	18.2	—
Juniper	Junos	18.3	—
Juniper	Junos	18.4	—
Juniper	Junos	19.1	—
Juniper	Junos	19.2	—
Juniper	Junos	19.3	—
Juniper	Junos	19.4	R1
Juniper	Junos	20.1	R1
Juniper	Junos	20.2	R1

References

https://kb.juniper.net/JSA11111Vendor Advisory
https://kb.juniper.net/JSA11111Vendor Advisory

Timeline

Published: Jan 15, 2021
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2021-0221?

In an EVPN/VXLAN scenario, if an IRB interface with a virtual gateway address (VGA) is configured on a PE, a traffic loop may occur upon receipt of specific IP multicast traffic. The traffic loop will cause interface traffic to increase abnormally, ultimately leading to a Denial of Service (DoS) in packet processing. The following command could be used to monitor the interface traffic: user@junos> monitor interface traffic Interface Link Input packets (pps) Output packets (pps) et-0/0/1 Up 6492089274364 (70994959) 6492089235319 (70994956) et-0/0/25 Up 343458103 (1) 156844 (0) ae0 Up 9132519197257 (70994959) 9132519139454 (70994956) This issue affects Juniper Networks Junos OS on QFX Series: all versions prior to 17.3R3-S10; 17.4 versions prior to 17.4R2-S12, 17.4R3-S3; 18.1 versions prior to 18.1R3-S11; 18.2 versions prior to 18.2R3-S6; 18.3 versions prior to 18.3R3-S4; 18.4 versions prior to 18.4R2-S5, 18.4R3-S5; 19.1 versions prior to 19.1R1-S6, 19.1R2-S2, 19.1R3-S3; 19.2 versions prior to 19.2R1-S5, 19.2R3-S1; 19.3 versions prior to 19.3R2-S5, 19.3R3; 19.4 versions prior to 19.4R2-S2, 19.4R3; 20.1 versions prior to 20.1R2; 20.2 versions prior to 20.2R1-S2, 20.2R2.

How severe is CVE-2021-0221?

CVE-2021-0221 has a CVSS score of 6.5/10 (MEDIUM severity). The EPSS model estimates a 0.51% probability of exploitation in the next 30 days.

How do I fix CVE-2021-0221?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.