2020-10 Security Bulletin: Junos OS: EX2300 Series: High CPU load due to receipt of specific multicast packets on layer 2 interface (CVE-2020-1668)

Product Affected:

This issue affects Junos OS 18.1, 18.2, 18.3, 18.4, 19.1, 19.2, 19.3, 19.4, 20.1. Affected platforms: EX2300 Series.

Problem:

On Juniper Networks EX2300 Series, receipt of a stream of specific multicast packets by the layer2 interface can cause high CPU load, which could lead to traffic interruption.

This issue occurs when multicast packets are received by the layer 2 interface.

To check if the device has high CPU load due to this issue, the administrator can issue the following command:

user@host> show chassis routing-engine
           Routing Engine status:
           ...
           Idle 2 percent

the Idle value shows as low (2 % in the example above), and also the following command:

user@host> show system processes summary
...
PID USERNAME PRI NICE SIZE RES STATE TIME WCPU COMMAND
11639 root 52 0 283M 11296K select 12:15 44.97% eventd
11803 root 81 0 719M 239M RUN 251:12 31.98% fxpc

the eventd and the fxpc processes might use higher WCPU percentage (respectively 44.97% and 31.98% in the above example).

This issue affects Juniper Networks Junos OS on EX2300 Series:

18.1 versions prior to 18.1R3-S11;
18.2 versions prior to 18.2R3-S5;
18.3 versions prior to 18.3R2-S4, 18.3R3-S3;
18.4 versions prior to 18.4R2-S5, 18.4R3-S4;
19.1 versions prior to 19.1R3-S2;
19.2 versions prior to 19.2R1-S5, 19.2R3;
19.3 versions prior to 19.3R2-S4, 19.3R3;
19.4 versions prior to 19.4R1-S3, 19.4R2-S1, 19.4R3;
20.1 versions prior to 20.1R1-S2, 20.1R2.

Juniper SIRT is not aware of any malicious exploitation of this vulnerability.

This issue was seen during production usage.

This issue has been assigned CVE-2020-1668.

Solution:

The following software releases have been updated to resolve this specific issue: Junos OS 18.1R3-S11, 18.2R3-S5, 18.3R2-S4, 18.3R3-S3, 18.4R2-S5, 18.4R3-S4, 19.1R3-S2, 19.2R1-S5, 19.2R3, 19.3R2-S4, 19.3R3, 19.4R1-S3, 19.4R2-S1, 19.4R3, 20.1R1-S2, 20.1R2, 20.2R1, and all subsequent releases.

This issue is being tracked as 1491905.

Workaround:

There are no available workarounds for this issue.

Implementation:

Software releases or updates are available for download at https://www.juniper.net/support/downloads/.

Modification History:

2020-10-14: Initial Publication.

CVSS Score:

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

Severity Level:

Medium

Severity Assessment:

Information for how Juniper Networks uses CVSS can be found at KB 16446 "Common Vulnerability Scoring System (CVSS) and Juniper's Security Advisories."

Knowledge Base