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CVE-2021-31377

Junos OS: A local authenticated attacker can cause RPD to core

Medium5.5EPSS 0.20%
Published
Updated
Reserved
Assigned by
juniper

Description

An Incorrect Permission Assignment for Critical Resource vulnerability of a certain file in the filesystem of Junos OS allows a local authenticated attacker to cause routing process daemon (RPD) to crash and restart, causing a Denial of Service (DoS). Repeated actions by the attacker will create a sustained Denial of Service (DoS) condition. 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; 18.1 versions prior to 18.1R3-S13; 18.2 versions prior to 18.2R3-S8; 18.3 versions prior to 18.3R3-S5; 18.4 versions prior to 18.4R2-S8, 18.4R3-S7; 19.1 versions prior to 19.1R2-S3, 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-S2; 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 20.3R3; 20.4 versions prior to 20.4R1-S1, 20.4R2.

Scores

CVSS scores of CVE-2021-31377, by who scored it
Scored byCVSSScoreVector
juniperCNA (assigner)3.1Medium5.5CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
NVDNVD · Modified3.1Medium5.5CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
EPSS (exploitation in 30 days)
0.20% · top 90% 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 5.5.

Weakness

Affected products

  • Juniper Networks · Junos OS

    • affected 15.1 – < 15.1R7-S9
    • affected 17.3 – < 17.3R3-S12
    • affected 17.4 – < 17.4R2-S13, 17.4R3-S5
    • affected 18.1 – < 18.1R3-S13
    • affected 18.2 – < 18.2R3-S8
    • affected 18.3 – < 18.3R3-S5
    • affected 18.4 – < 18.4R2-S8, 18.4R3-S7
    • affected 19.1 – < 19.1R2-S3, 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-S2
    • affected 20.1 – < 20.1R2-S2, 20.1R3
    • affected 20.2 – < 20.2R2-S3, 20.2R3
    • affected 20.3 – < 20.3R3
    • affected 20.4 – < 20.4R1-S1, 20.4R2

What to do

Solution: The following software releases have been updated to resolve this specific issue: 15.1R7-S9, 17.3R3-S12, 17.4R2-S13, 17.4R3-S5, 18.1R3-S13, 18.2R3-S8, 18.3R3-S5, 18.4R2-S8, 18.4R3-S7, 19.1R3-S5, 19.2R3-S2, 19.3R2-S6, 19.3R3-S2, 19.4R1-S4, 19.4R2-S4, 19.4R3-S2, 20.1R2-S2, 20.1R3, 20.2R2-S3, 20.2R3, 20.3R3, 20.4R1-S1, 20.4R2, 21.1R1, and all subsequent releases.

Workaround: To reduce the risk of exploitation of this issue, use access lists or firewall filters to limit access to only trusted administrative networks, hosts and users.

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 .