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2021-07 Security Bulletin: Junos OS and Junos OS Evolved: A vulnerability allows a network based unauthenticated attacker which sends a high rate of specific traffic to cause a partial Denial of Service (CVE-2021-0291)

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Article ID: JSA11193 SECURITY_ADVISORIES Last Updated: 14 Jul 2021Version: 2.0
Product Affected:
This issue affects Junos OS 15.1, 17.3, 17.4, 18.3, 18.4, 19.1, 19.2, 19.3, 19.4, 20.1, 20.2, 20.3. This issue affects all versions of Junos OS Evolved.
Problem:

An Exposure of System Data vulnerability in Juniper Networks Junos OS and Junos OS Evolved, where a sensitive system-level resource is not being sufficiently protected, allows a network-based unauthenticated attacker to send specific traffic which partially reaches this resource. A high rate of specific traffic may lead to a partial Denial of Service (DoS) as the CPU utilization of the RE is significantly increased.

The SNMP Agent Extensibility (agentx) process should only be listening to TCP port 705 on the internal routing instance. External connections destined to port 705 should not be allowed.

This issue affects:

Juniper Networks Junos OS:

  • 15.1 versions prior to 15.1R7-S9;
  • 17.3 versions prior to 17.3R3-S12;
  • 17.4 versions prior to 17.4R2-S13, 17.4R3-S5;
  • 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 19.2R3-S2;
  • 19.3 versions prior to 19.3R2-S6, 19.3R3-S2;
  • 19.4 versions prior to 19.4R1-S4, 19.4R2-S4, 19.4R3;
  • 20.1 versions prior to 20.1R2;
  • 20.2 versions prior to 20.2R2;
  • 20.3 versions prior to 20.3R2.

Juniper Networks Junos OS Evolved versions prior to 20.3R2-EVO.

This issue does not affect Juniper Networks Junos OS versions prior to 13.2R1.


SRX and EX platforms are affected by default, whereas all other platforms running Junos OS and Junos OS Evolved are only affected if:

[ snmp subagent tcp ]

is configured.


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-2021-0291.
 

Solution:

The following software releases have been updated to resolve this specific issue:

Junos OS: 15.1R7-S9, 17.3R3-S12, 17.4R2-S13, 17.4R3-S5, 18.3R3-S5, 18.4R2-S8, 19.1R3-S5, 19.2R3-S2, 19.3R2-S6, 19.3R3-S2, 19.4R1-S4, 19.4R2-S4, 19.4R3, 20.1R2, 20.2R2, 20.2R3, 20.3R2, 20.4R1, and all subsequent releases.

Junos OS Evolved: 20.3R2-EVO, 20.4R1-EVO, and all subsequent releases.

This issue is being tracked as 1536350.
 

Workaround:
Use access lists or firewall filters to deny access to TCP port 705.
 
Implementation:
Software releases or updates are available for download at https://support.juniper.net/support/downloads/
 
Modification History:
2021-07-14: Initial Publication.

CVSS Score:
6.5 (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/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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