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CVE-2021-0258

Junos OS: Kernel panic upon receipt of specific TCPv6 packet on management interface

Medium5.9EPSS 0.65%
Published
Updated
Reserved
Assigned by
juniper

Description

A vulnerability in the forwarding of transit TCPv6 packets received on the Ethernet management interface of Juniper Networks Junos OS allows an attacker to trigger a kernel panic, leading to a Denial of Service (DoS). Continued receipt and processing of these transit packets will create a sustained Denial of Service (DoS) condition. This issue only occurs when TCPv6 packets are routed through the management interface. Other transit traffic, and traffic destined to the management interface, are unaffected by this vulnerability. This issue was introduced as part of a TCP Parallelization feature added in Junos OS 17.2, and affects systems with concurrent network stack enabled. This feature is enabled by default, but can be disabled (see WORKAROUND section below). This issue affects Juniper Networks Junos OS: 17.2 versions prior to 17.2R3-S4; 17.3 versions prior to 17.3R3-S9; 17.4 versions prior to 17.4R2-S11, 17.4R3-S2; 18.1 versions prior to 18.1R3-S11; 18.2 versions prior to 18.2R3-S5; 18.3 versions prior to 18.3R2-S4, 18.3R3-S3; 18.4 versions prior to 18.4R2-S5, 18.4R3-S4; 19.1 versions prior to 19.1R2-S2, 19.1R3; 19.2 versions prior to 19.2R1-S5, 19.2R2; 19.3 versions prior to 19.3R2-S4, 19.3R3; 19.4 versions prior to 19.4R1-S3, 19.4R2. This issue does not affect Juniper Networks Junos OS versions prior to 17.2R1.

Scores

CVSS scores of CVE-2021-0258, by who scored it
Scored byCVSSScoreVector
juniperCNA (assigner)3.1Medium5.9CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
NVDNVD · Modified3.1Medium5.9CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
EPSS (exploitation in 30 days)
0.65% · top 49% 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 5.9.

Weakness

Affected products

  • Juniper Networks · Junos OS

    • unaffected 17.2 – < 17.2R1
    • affected 17.3 – < 17.3R3-S9
    • affected 17.4 – < 17.4R2-S11, 17.4R3-S2
    • affected 18.1 – < 18.1R3-S11
    • affected 18.2 – < 18.2R3-S5
    • affected 18.3 – < 18.3R2-S4, 18.3R3-S3
    • affected 18.4 – < 18.4R2-S5, 18.4R3-S4
    • affected 19.1 – < 19.1R2-S2, 19.1R3
    • affected 19.2 – < 19.2R1-S5, 19.2R2
    • affected 19.3 – < 19.3R2-S4, 19.3R3
    • affected 19.4 – < 19.4R1-S3, 19.4R2

What to do

Solution: The following software releases have been updated to resolve this specific issue: Junos OS 17.2R3-S4, 17.3R3-S9, 17.4R2-S11, 17.4R3-S2, 18.1R3-S11, 18.2R3-S5, 18.3R2-S4, 18.3R3-S3, 18.4R2-S5, 18.4R3-S4, 19.1R2-S2, 19.1R3, 19.2R1-S5, 19.2R2, 19.3R2-S4, 19.3R3, 19.4R1-S3, 19.4R2, 20.1R1, and all subsequent releases.

Workaround: Disable TCP Parallelization: set system kernel-smp-features disable-concurrent-network-stack

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

References (1)

Sources

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Record last updated .