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CVE-2021-31350

Junos OS and Junos OS Evolved: Privilege escalation vulnerability in Juniper Extension Toolkit (JET)

High7.5EPSS 0.87%
Published
Updated
Reserved
Assigned by
juniper

Description

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 system. 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: 18.4 versions prior to 18.4R1-S8, 18.4R2-S8, 18.4R3-S8; 19.1 versions prior to 19.1R2-S3, 19.1R3-S5; 19.2 versions prior to 19.2R1-S7, 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-S3; 20.1 versions prior to 20.1R2-S2, 20.1R3; 20.2 versions prior to 20.2R2-S3, 20.2R3; 20.3 versions prior to 20.3R2-S1, 20.3R3; 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: All versions prior to 20.4R2-EVO; 21.1-EVO versions prior to 21.1R2-EVO.

Timeline

  1. ID reserved

    By juniper

  2. · 6 months later

    Published

  3. · 3 years later

    Record updated

Changes after publication (a new score, a public exploit, EPSS crossing 1, 10 or 50 %, leaving KEV) are kept since November 2026; earlier ones are not known.

Scores

CVSS scores of CVE-2021-31350, by who scored it
Scored byCVSSScoreVector
juniperCNA (assigner)3.1High7.5CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
NVDNVD · Modified3.1High8.8CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
EPSS (exploitation in 30 days)
0.87% · top 41% of all CVEs (7 Nov 2026)
Loading the EPSS history…

The list uses the assigner's score when there is one, then CISA's, then NVD's: High 7.5.

Weakness

Affected products

  • Juniper Networks · Junos OS

    • unaffected unspecified – < 18.4R1
    • affected 18.4 – < 18.4R1-S8, 18.4R2-S8, 18.4R3-S8
    • affected 19.1 – < 19.1R2-S3, 19.1R3-S5
    • affected 19.2 – < 19.2R1-S7, 19.2R3-S2
    • affected 19.3 – < 19.3R2-S6, 19.3R3-S2
    • affected 19.4 – < 19.4R1-S4, 19.4R2-S4, 19.4R3-S3
    • affected 20.1 – < 20.1R2-S2, 20.1R3
    • affected 20.2 – < 20.2R2-S3, 20.2R3
    • affected 20.3 – < 20.3R2-S1, 20.3R3
    • affected 20.4 – < 20.4R2

  • Juniper Networks · Junos OS Evolved

    • affected unspecified – < 20.4R2-EVO
    • affected 21.1-EVO – < 21.1R2-EVO

What to do

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

Workaround: Use access lists or firewall filters to limit access to the device via gRPC only from trusted hosts and from trusted administrators

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

References (1)

Sources

The same CVE in the primary databases and aggregators, to check against.

Badge for a README or a ticket

CVE-2021-31350 badge
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Record last updated .