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2021-10 Security Bulletin: Junos OS: QFX Series and PTX Series: FPC resource usage increases when certain packets are processed which are being VXLAN encapsulated (CVE-2021-31361)

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Article ID: JSA11223 SECURITY_ADVISORIES Last Updated: 13 Oct 2021Version: 3.0
Product Affected:
This issue affects all versions of Junos OS. Affected platforms: QFX Series and PTX Series.
Problem:

An Improper Check for Unusual or Exceptional Conditions vulnerability combined with Improper Handling of Exceptional Conditions in Juniper Networks Junos OS on QFX Series and PTX Series allows an unauthenticated network based attacker to cause increased FPC CPU utilization by sending specific IP packets which are being VXLAN encapsulated leading to a partial Denial of Service (DoS).

Continued receipted of these specific traffic will create a sustained Denial of Service (DoS) condition.

This issue affects:
Juniper Networks Junos OS on QFX Series:

  • All versions prior to 17.3R3-S11;
  • 17.4 versions prior to 17.4R2-S13, 17.4R3-S4;
  • 18.1 versions prior to 18.1R3-S12;
  • 18.2 versions prior to 18.2R2-S8, 18.2R3-S7;
  • 18.3 versions prior to 18.3R3-S4;
  • 18.4 versions prior to 18.4R1-S8, 18.4R2-S7, 18.4R3-S7;
  • 19.1 versions prior to 19.1R1-S6, 19.1R2-S2, 19.1R3-S4;
  • 19.2 versions prior to 19.2R1-S6, 19.2R3-S2;
  • 19.3 versions prior to 19.3R3-S1;
  • 19.4 versions prior to 19.4R2-S3, 19.4R3-S1;
  • 20.1 versions prior to 20.1R2, 20.1R3;
  • 20.2 versions prior to 20.2R2, 20.2R3;
  • 20.3 versions prior to 20.3R1-S1, 20.3R2.

Juniper Networks Junos OS on PTX Series:

  • All versions prior to 18.4R3-S9;
  • 19.1 versions prior to 19.1R3-S6;
  • 19.2 versions prior to 19.2R1-S7, 19.2R3-S3;
  • 19.3 versions prior to 19.3R2-S6, 19.3R3-S3;
  • 19.4 versions prior to 19.4R1-S4, 19.4R3-S5;
  • 20.1 versions prior to 20.1R2-S2, 20.1R3;
  • 20.2 versions prior to 20.2R3-S1;
  • 20.3 versions prior to 20.3R2-S1, 20.3R3;
  • 20.4 versions prior to 20.4R2-S1, 20.4R3;
  • 21.1 versions prior to 21.1R1-S1, 21.1R2.

An minimal example VXLAN configuration affected would be:

set bridge-domains vlan-20 vxlan vni 10
set bridge-domains vlan-20 vlan-id 10
set bridge-domains vlan-20 interface xe-1/0/1.0
set interfaces xe-1/0/1 vlan-tagging
set interfaces xe-1/0/1 encapsulation flexible-ethernet-services
set interfaces xe-1/0/1 unit 0 encapsulation vlan-bridge
set interfaces xe-1/0/1 unit 0 vlan-id 10

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-2021-31361.

Solution:

The following software releases have been updated to resolve this specific issue for QFX Series: 17.3R3-S11, 17.4R2-S13, 17.4R3-S4, 18.1R3-S12, 18.2R2-S8, 18.2R3-S7, 18.3R3-S4, 18.4R1-S8, 18.4R2-S7, 18.4R3-S7, 19.1R1-S6, 19.1R2-S2, 19.1R3-S4, 19.2R1-S6, 19.2R3-S2, 19.3R3-S1, 19.4R2-S3, 19.4R3-S1, 20.1R2, 20.1R3, 20.2R2, 20.2R3, 20.3R1-S1, 20.3R2, 20.4R1, and all subsequent releases.

The following software releases have been updated to resolve this specific issue for PTX Series: 18.4R3-S9, 19.1R3-S6, 19.2R1-S7, 19.2R3-S3, 19.3R2-S6, 19.3R3-S3, 19.4R1-S4, 19.4R3-S5, 20.1R2-S2, 20.1R3, 20.2R3-S1, 20.3R2-S1, 20.3R3, 20.4R2-S1, 20.4R3, 21.1R1-S1, 21.1R2, 21.2R1, and all subsequent releases.

This issue is being tracked as 1490063 and 1584197.

Workaround:
There are no viable workarounds for this issue.
Implementation:
Software releases or updates are available for download at https://support.juniper.net/support/downloads/
Modification History:
2021-10-13: Initial Publication.
CVSS Score:
5.3 (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L)
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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