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AUSCERT External Security Bulletin Redistribution
JSA11219 - 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)
15 October 2021
AusCERT Security Bulletin Summary
Product: Junos OS
Junos OS Evolved
Publisher: Juniper Networks
Operating System: Juniper
Impact/Access: Execute Arbitrary Code/Commands -- Remote/Unauthenticated
Denial of Service -- Remote/Unauthenticated
CVE Names: CVE-2021-31354
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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
Last Updated: 13 Oct 2021
Version : 1.0
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
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:
o 19.2 versions prior to 19.2R3-S3;
o 19.3 versions prior to 19.3R3-S3;
o 20.1 versions prior to 20.1R2-S2, 20.1R3-S1;
o 20.2 versions prior to 20.2R3-S2;
o 20.3 versions prior to 20.3R3;
o 20.4 versions prior to 20.4R3;
o 21.1 versions prior to 21.1R2.
Juniper Networks Junos OS Evolved 20.1R1-EVO and later versions, prior to
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
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
user@junos# set system license standalone-mode
Software releases or updates are available for download at https://
2021-10-13: Initial Publication.
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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