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2020-10 Security Bulletin: Junos OS: EX4300 Series: High CPU load due to receipt of specific IPv4 packets (CVE-2020-1670)

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Article ID: JSA11067 SECURITY_ADVISORIES Last Updated: 29 Oct 2020Version: 2.0
Product Affected:
This issue affects Junos OS 17.3, 17.4, 18.1, 18.2, 18.3, 18.4, 19.1, 19.2, 19.3, 19.4, 20.1. Affected platforms: EX4300 series.
Problem:

On Juniper Networks EX4300 Series, receipt of a stream of specific IPv4 packets can cause Routing Engine (RE) high CPU load, which could lead to network protocol operation issue and traffic interruption.

This specific packets can originate only from within the broadcast domain where the device is connected.

This issue occurs when the packets enter to the IRB interface.

Only IPv4 packets can trigger this issue. IPv6 packets cannot trigger this issue.
 

This issue affects Juniper Networks Junos OS on EX4300 series:

  • 17.3 versions prior to 17.3R3-S9;
  • 17.4 versions prior to 17.4R2-S11, 17.4R3-S2;
  • 18.1 versions prior to 18.1R3-S10;
  • 18.2 versions prior to 18.2R3-S4;
  • 18.3 versions prior to 18.3R2-S4, 18.3R3-S2;
  • 18.4 versions prior to 18.4R2-S4, 18.4R3-S2;
  • 19.1 versions prior to 19.1R2-S2, 19.1R3-S1;
  • 19.2 versions prior to 19.2R1-S5, 19.2R2-S1, 19.2R3;
  • 19.3 versions prior to 19.3R2-S4, 19.3R3;
  • 19.4 versions prior to 19.4R1-S3, 19.4R2;
  • 20.1 versions prior to 20.1R1-S3, 20.1R2.
     

The example of the configuration stanza affected by this issue is as follows:

[interfaces irb unit <UNIT_NUMBER>]

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-2020-1670.

Solution:

The following software releases have been updated to resolve this specific issue: 17.3R3-S9, 17.4R2-S11, 17.4R3-S2, 18.1R3-S10, 18.2R3-S4, 18.3R2-S4, 18.3R3-S2, 18.4R2-S4, 18.4R3-S2, 19.1R2-S2, 19.1R3-S1, 19.2R1-S5, 19.2R2-S1, 19.2R3, 19.3R2-S4, 19.3R3, 19.4R1-S3, 19.4R2, 20.1R1-S3, 20.1R2, 20.2R1 and all subsequent releases.

This issue is being tracked as 1495129.

Workaround:

There are no viable 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."

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