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CVE-2021-0291

Junos OS and Junos OS Evolved: A vulnerability allows a network based unauthenticated attacker which sends a high rate of specific traffic to cause a partial Denial of Service

Medium6.5EPSS 1.0%
Published
Updated
Reserved
Assigned by
juniper

Description

An Exposure of System Data vulnerability in Juniper Networks Junos OS and Junos OS Evolved, where a sensitive system-level resource is not being sufficiently protected, allows a network-based unauthenticated attacker to send specific traffic which partially reaches this resource. A high rate of specific traffic may lead to a partial Denial of Service (DoS) as the CPU utilization of the RE is significantly increased. The SNMP Agent Extensibility (agentx) process should only be listening to TCP port 705 on the internal routing instance. External connections destined to port 705 should not be allowed. This issue affects: Juniper Networks Junos OS: 15.1 versions prior to 15.1R7-S9; 17.3 versions prior to 17.3R3-S12; 17.4 versions prior to 17.4R2-S13, 17.4R3-S5; 18.3 versions prior to 18.3R3-S5; 18.4 versions prior to 18.4R2-S8; 19.1 versions prior to 19.1R3-S5; 19.2 versions prior to 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; 20.1 versions prior to 20.1R2; 20.2 versions prior to 20.2R2; 20.3 versions prior to 20.3R2. Juniper Networks Junos OS Evolved versions prior to 20.3R2-EVO. This issue does not affect Juniper Networks Junos OS versions prior to 13.2R1.

Timeline

  1. ID reserved

    By juniper

  2. · 9 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-2021-0291, by who scored it
Scored byCVSSScoreVector
juniperCNA (assigner)3.1Medium6.5CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:L
NVDNVD · Modified3.1Medium6.5CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:L
EPSS (exploitation in 30 days)
1.0% · top 37% 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: Medium 6.5.

Weakness

Affected products

  • Juniper Networks · Junos OS

    • unaffected unspecified – < 13.2R1
    • affected 15.1 – < 15.1R7-S9
    • affected 17.3 – < 17.3R3-S12
    • affected 17.4 – < 17.4R2-S13, 17.4R3-S5
    • affected 18.3 – < 18.3R3-S5
    • affected 18.4 – < 18.4R2-S8, 18.4R3-S9
    • affected 19.1 – < 19.1R3-S5
    • affected 19.2 – < 19.2R3-S2
    • affected 19.3 – < 19.3R2-S6, 19.3R3-S2
    • affected 19.4 – < 19.4R1-S4, 19.4R2-S4, 19.4R3
    • affected 20.1 – < 20.1R2
    • affected 20.2 – < 20.2R2
    • affected 20.3 – < 20.3R2

  • Juniper Networks · Junos OS Evolved

    • affected unspecified – < 20.3R2-EVO

What to do

Solution: The following software releases have been updated to resolve this specific issue: Junos OS: 15.1R7-S9, 17.3R3-S12, 17.4R2-S13, 17.4R3-S5, 18.3R3-S5, 18.4R2-S8, 19.1R3-S5, 19.2R3-S2, 19.3R2-S6, 19.3R3-S2, 19.4R1-S4, 19.4R2-S4, 19.4R3, 20.1R2, 20.2R2, 20.2R3, 20.3R2, 20.4R1, and all subsequent releases. Junos OS Evolved: 20.3R2-EVO, 20.4R1-EVO, and all subsequent releases.

Workaround: Use access lists or firewall filters to deny access to TCP port 705.

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.

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Record last updated .