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2021-10 Security Bulletin: Junos OS and Junos OS Evolved: A vulnerability in the Juniper Agile License Client may allow an attacker to perform Remote Code Execution (RCE) (CVE-2021-31354)



Article ID: JSA11219 SECURITY_ADVISORIES Last Updated: 13 Oct 2021Version: 1.0
Product Affected:
This issue affects Junos OS 19.2, 19.3, 20.1, 20.2, 20.3, 20.4, 21.1. This issue affects Junos OS Evolved 20.1R1-EVO through 21.2R2-EVO.

An Out Of Bounds (OOB) access vulnerability in the handling of responses by a Juniper Agile License (JAL) Client in Juniper Networks Junos OS and Junos OS Evolved, configured in Network Mode (to use Juniper Agile License Manager) may allow an attacker to cause a partial Denial of Service (DoS), or lead to remote code execution (RCE). The vulnerability exists in the packet parsing logic on the client that processes the response from the server using a custom protocol. An attacker with control of a JAL License Manager, or with access to the local broadcast domain, may be able to spoof a new JAL License Manager and/or craft a response to the Junos OS License Client, leading to exploitation of this vulnerability.

This issue only affects Junos systems configured in Network Mode. Systems that are configured in Standalone Mode (the default mode of operation for all systems) are not vulnerable to this issue.

This issue affects:

Juniper Networks Junos OS:

  • 19.2 versions prior to 19.2R3-S3;
  • 19.3 versions prior to 19.3R3-S3;
  • 20.1 versions prior to 20.1R2-S2, 20.1R3-S1;
  • 20.2 versions prior to 20.2R3-S2;
  • 20.3 versions prior to 20.3R3;
  • 20.4 versions prior to 20.4R3;
  • 21.1 versions prior to 21.1R2.

Juniper Networks Junos OS Evolved 20.1R1-EVO and later versions, prior to 21.2R2-EVO.

This issue does not affect Juniper Networks Junos OS versions prior to 19.2R1.

Systems vulnerable to this issue will have the Junos License Client set to Network Mode as follows:

[system license network-mode]

Juniper SIRT is not aware of any malicious exploitation of this vulnerability.

This issue was discovered during external security research.

This issue has been assigned CVE-2021-31354.


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

Junos OS 19.3R3-S3, 20.1R2-S2, 20.1R3-S1, 20.2R3-S2, 20.3R3, 20.4R3, 21.1R2, 21.2R1, and all subsequent releases.

Junos OS Evolved 21.2R2-EVO, 21.3R1-EVO, and all subsequent releases.

This issue is being tracked as 1582419.


Disable Network Mode and configure the Junos License Client to use Standalone Mode:

user@junos# set system license standalone-mode

Software releases or updates are available for download at
Modification History:
2021-10-13: Initial Publication.

CVSS Score:
7.1 (CVSS:3.1/AV:A/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:L)
Severity Level:
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."
Juniper SIRT would like to acknowledge and thank The UK's National Cyber Security Centre (NCSC) for responsibly reporting this vulnerability.

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