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   JSA11215 - 2021-10 Security Bulletin: Junos OS and Junos OS Evolved:
          Privilege escalation vulnerability in Juniper Extension
                      Toolkit (JET) (CVE-2021-31350)
                              15 October 2021


        AusCERT Security Bulletin Summary

Product:           Junos OS
                   Junos OS Evolved
Publisher:         Juniper Networks
Operating System:  Juniper
Impact/Access:     Root Compromise -- Existing Account
Resolution:        Patch/Upgrade
CVE Names:         CVE-2021-31350  

Original Bulletin: 

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2021-10 Security Bulletin: Junos OS and Junos OS Evolved: Privilege escalation vulnerability in Juniper Extension Toolkit (JET) (CVE-2021-31350)

Article ID  : JSA11215
Last Updated: 13 Oct 2021
Version     : 1.0

Product Affected:
This issue affects Junos OS 18.4, 19.1, 19.2, 19.3, 19.4, 20.1, 20.2, 20.3,
20.4. This issue affects all versions of Junos OS Evolved.

An Improper Privilege Management vulnerability in the gRPC framework, used by
the Juniper Extension Toolkit (JET) API on Juniper Networks Junos OS and Junos
OS Evolved, allows a network-based, low-privileged authenticated attacker to
perform operations as root, leading to complete compromise of the targeted

The issue is caused by the JET service daemon (jsd) process authenticating the
user, then passing configuration operations directly to the management daemon
(mgd) process, which runs as root.

This issue affects Juniper Networks Junos OS:

  o 18.4 versions prior to 18.4R1-S8, 18.4R2-S8, 18.4R3-S8;
  o 19.1 versions prior to 19.1R2-S3, 19.1R3-S5;
  o 19.2 versions prior to 19.2R1-S7, 19.2R3-S2;
  o 19.3 versions prior to 19.3R2-S6, 19.3R3-S2;
  o 19.4 versions prior to 19.4R1-S4, 19.4R2-S4, 19.4R3-S3;
  o 20.1 versions prior to 20.1R2-S2, 20.1R3;
  o 20.2 versions prior to 20.2R2-S3, 20.2R3;
  o 20.3 versions prior to 20.3R2-S1, 20.3R3;
  o 20.4 versions prior to 20.4R2.

This issue does not affect Juniper Networks Junos OS versions prior to 18.4R1.

Juniper Networks Junos OS Evolved:

  o All versions prior to 20.4R2-EVO;
  o 21.1-EVO versions prior to 21.1R2-EVO.

The following is an example of enabling gRPC in Junos:

set system services extension-service request-response grpc ssl

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

This issue was found during internal product security testing or research.

This issue has been assigned CVE-2021-31350 .


The following software releases have been updated to resolve this specific

Junos OS 18.4R1-S8, 18.4R2-S8, 18.4R3-S8, 19.1R2-S3, 19.1R3-S5, 19.2R1-S7,
19.2R3-S2, 19.3R2-S6, 19.3R3-S2, 19.4R1-S4, 19.4R2-S4, 19.4R3-S3, 20.1R2-S2,
20.1R3, 20.2R2-S3, 20.2R3, 20.3R2-S1, 20.3R3, 20.4R2, 21.1R1, and all
subsequent releases.

Junos OS Evolved 20.4R2-EVO, 21.1R2-EVO, 21.2R1-EVO, and all subsequent

This issue is being tracked as 1578302 .

Use access lists or firewall filters to limit access to the device via gRPC
only from trusted hosts and from trusted administrators
Software releases or updates are available for download at https://
Modification History:

2021-10-13: Initial Publication.

CVSS Score:
7.5 (CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H)
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."

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