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2021-10 Security Bulletin: Junos OS and Junos OS Evolved: An IS-IS adjacency might be taken down if a bad hello PDU is received for an existing adjacency causing a DoS (CVE-2021-31362)

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Article ID: JSA11224 SECURITY_ADVISORIES Last Updated: 13 Oct 2021Version: 3.0
Product Affected:
This issue affects all versions of Junos OS and all versions of Junos OS Evolved.
Problem:

A Protection Mechanism Failure vulnerability in RPD (routing protocol daemon) of Juniper Networks Junos OS and Junos OS Evolved allows an adjacent unauthenticated attacker to cause established IS-IS adjacencies to go down by sending a spoofed hello PDU leading to a Denial of Service (DoS) condition.

Continued receipted of these spoofed PDUs will create a sustained Denial of Service (DoS) condition.

This issue affects:

Juniper Networks Junos OS

  • All versions prior to 18.2R3-S8;
  • 18.3 versions prior to 18.3R3-S5;
  • 18.4 versions prior to 18.4R3-S9;
  • 19.1 versions prior to 19.1R3-S7;
  • 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 19.4R3-S3;
  • 20.1 versions prior to 20.1R3;
  • 20.2 versions prior to 20.2R3;
  • 20.3 versions prior to 20.3R3;
  • 20.4 versions prior to 20.4R2.

Juniper Networks Junos OS Evolved

  • All versions prior to 20.4R2-EVO;
  • 21.1 versions prior to 21.1R2-EVO.
[ protocols isis interface ]

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-2021-31362.

Solution:

The following software releases have been updated to resolve this specific issue in JUNOS OS: 18.2R3-S8, 18.3R3-S5, 18.4R3-S9, 19.1R3-S7, 19.2R1-S7, 19.2R3-S3, 19.3R2-S6, 19.3R3-S2, 19.4R3-S3, 20.1R3, 20.2R3, 20.3R3, 20.4R2, 21.1R1, and all subsequent releases.

The following software releases have been updated to resolve this specific issue in JUNOS OS Evolved: 20.4R2-EVO, 21.1R2-EVO, 21.2R1-EVO, and all subsequent releases.

This issue is being tracked as 1556575.

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:
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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