CVE-2021-31354: 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 Juno...

Description

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: version 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.

Metrics

CVSS 3.1

8.8/10

CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

EPSS Probability

0.61%

44.6th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

Affected Software

Vendor	Product	Versions	Update
Juniper	Junos	19.2	—
Juniper	Junos	19.3	—
Juniper	Junos	20.1	R1
Juniper	Junos	20.2	R1
Juniper	Junos	20.3	R1
Juniper	Junos	20.4	R1
Juniper	Junos	21.1	R1
Juniper	Junos Os Evolved	20.1	R1
Juniper	Junos Os Evolved	20.2	—
Juniper	Junos Os Evolved	20.3	—
Juniper	Junos Os Evolved	20.4	R1
Juniper	Junos Os Evolved	21.1	—
Juniper	Junos Os Evolved	21.2	R1

References

https://kb.juniper.net/JSA11219Vendor Advisory
https://kb.juniper.net/JSA11219Vendor Advisory

Timeline

Published: Oct 19, 2021
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2021-31354?

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: version 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.

How severe is CVE-2021-31354?

CVE-2021-31354 has a CVSS score of 8.8/10 (HIGH severity). The EPSS model estimates a 0.61% probability of exploitation in the next 30 days.

How do I fix CVE-2021-31354?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.