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2021-10 Security Bulletin: Junos OS: EX2300 Series, EX3400 Series, and ACX710 might become unresponsive if the out-of-band management port receives a flood of traffic (CVE-2021-31368)

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Article ID: JSA11230 SECURITY_ADVISORIES Last Updated: 13 Oct 2021Version: 1.0
Product Affected:
This issue affects all versions of Junos OS. Affected platforms: ACX710, EX2300 Series, EX3400 Series
Problem:

An Uncontrolled Resource Consumption vulnerability in the kernel of Juniper Networks JUNOS OS allows an unauthenticated network based attacker to cause 100% CPU load and the device to become unresponsive by sending a flood of traffic to the out-of-band management ethernet port.

Continued receipted of a flood will create a sustained Denial of Service (DoS) condition. Once the flood subsides the system will recover by itself.

An indication that the system is affected by this issue would be that kernel and netisr process are shown to be using a lot of CPU cycles like in the following example output:

user@host> show system processes extensive
...
PID USERNAME PRI NICE SIZE RES STATE C TIME WCPU COMMAND
16 root -72 - 0K 304K WAIT 1 839:40 88.96% intr{swi1: netisr 0}
0 root 97 - 0K 160K RUN 1 732:43 87.99% kernel{bcm560xgmac0 que}

This issue affects Juniper Networks JUNOS OS on EX2300 Series, EX3400 Series, and ACX710:

  • All versions prior to 18.1R3-S13;
  • 18.2 versions prior to 18.2R3-S8;
  • 18.3 versions prior to 18.3R3-S5;
  • 18.4 versions prior to 18.4R2-S8, 18.4R3-S9;
  • 19.1 versions prior to 19.1R3-S5;
  • 19.2 versions prior to 19.2R1-S7, 19.2R3-S3;
  • 19.3 versions prior to 19.3R2-S6, 19.3R3-S2;
  • 19.4 versions prior to 19.4R1-S4, 19.4R3-S3;
  • 20.1 versions prior to 20.1R2-S2, 20.1R3;
  • 20.2 versions prior to 20.2R3;
  • 20.3 versions prior to 20.3R2-S1, 20.3R3;
  • 20.4 versions prior to 20.4R2.

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-2021-31368.

Solution:

The following software releases have been updated to resolve this specific issue: 18.1R3-S13, 18.3R3-S5, 18.4R2-S8, 18.4R3-S9, 19.1R3-S5, 19.2R1-S7, 19.2R3-S3, 19.3R2-S6, 19.3R3-S2, 19.4R1-S4, 19.4R3-S3, 20.1R2-S2, 20.1R3, 20.2R3, 20.3R2-S1, 20.3R3, 20.4R2, 21.1R1, and all subsequent releases.

This issue is being tracked as 1536800.

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:
7.5 (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H)
Severity Level:
High
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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