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CVE-2021-0244

Junos OS: A race condition in the storm control profile may allow an attacker to cause a Denial of Service condition

High7.4EPSS 0.64%
Published
Updated
Reserved
Assigned by
juniper

Description

A signal handler race condition exists in the Layer 2 Address Learning Daemon (L2ALD) of Juniper Networks Junos OS due to the absence of a specific protection mechanism to avoid a race condition which may allow an attacker to bypass the storm-control feature on devices. This issue is a corner case and only occurs during specific actions taken by an administrator of a device under certain specifics actions which triggers the event. The event occurs less frequently on devices which are not configured with Virtual Chassis configurations, and more frequently on devices configured in Virtual Chassis configurations. This issue is not specific to any particular Junos OS platform. An Indicator of Compromise (IoC) may be seen by reviewing log files for the following error message seen by executing the following show statement: show log messages | grep storm Result to look for: /kernel: GENCFG: op 58 (Storm Control Blob) failed; err 1 (Unknown) This issue affects: Juniper Networks Junos OS: 14.1X53 versions prior to 14.1X53-D49 on EX Series; 15.1 versions prior to 15.1R7-S6; 15.1X49 versions prior to 15.1X49-D191, 15.1X49-D200 on SRX Series; 16.1 versions prior to 16.1R7-S7; 16.2 versions prior to 16.2R2-S11, 16.2R3; 17.1 versions prior to 17.1R2-S11, 17.1R3; 17.2 versions prior to 17.2R2-S8, 17.2R3-S3; 17.3 versions prior to 17.3R2-S5, 17.3R3-S7; 17.4 versions prior to 17.4R2-S9, 17.4R3; 18.1 versions prior to 18.1R3-S5; 18.2 versions prior to 18.2R2-S6, 18.2R3; 18.3 versions prior to 18.3R1-S7, 18.3R2-S3, 18.3R3; 18.4 versions prior to 18.4R1-S5, 18.4R2; 19.1 versions prior to 19.1R1-S4, 19.1R2.

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-2021-0244, by who scored it
Scored byCVSSScoreVector
juniperCNA (assigner)3.1High7.4CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:N/I:N/A:H
NVDNVD · Modified3.1High7.4CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:N/I:N/A:H
EPSS (exploitation in 30 days)
0.64% · 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: High 7.4.

Weakness

Affected products

  • Juniper Networks · Junos OS

    • affected 14.1X53 – < 14.1X53-D49

  • Juniper Networks · Junos OS

    • affected 15.1 – < 15.1R7-S6
    • affected 16.1 – < 16.1R7-S7
    • affected 16.2 – < 16.2R2-S11, 16.2R3
    • affected 17.1 – < 17.1R2-S11, 17.1R3
    • affected 17.2 – < 17.2R2-S8, 17.2R3-S3
    • affected 17.3 – < 17.3R2-S5, 17.3R3-S7
    • affected 17.4 – < 17.4R2-S9, 17.4R3
    • affected 18.1 – < 18.1R3-S5
    • affected 18.2 – < 18.2R2-S6, 18.2R3
    • affected 18.3 – < 18.3R1-S7, 18.3R2-S3, 18.3R3
    • affected 18.4 – < 18.4R1-S5, 18.4R2
    • affected 19.1 – < 19.1R1-S4, 19.1R2

  • Juniper Networks · Junos OS

    • affected 15.1X49 – < 15.1X49-D191, 15.1X49-D200

What to do

Solution: The following software releases have been updated to resolve this specific issue: 14.1X53-D49, 15.1R7-S6, 15.1X49-D191, 15.1X49-D200, 15.1X53-D592, 16.1R7-S7, 16.1R8, 16.2R2-S11, 16.2R3, 17.1R2-S11, 17.1R3, 17.2R2-S8, 17.2R3-S3, 17.3R2-S5, 17.3R3-S7, 17.4R2-S9, 17.4R3, 18.1R3-S5, 18.2R2-S6, 18.2R3, 18.3R1-S7, 18.3R2-S3, 18.3R3, 18.4R1-S5, 18.4R2, 19.1R1-S4, 19.1R2, 19.2R1, and all subsequent releases.

Workaround: There are no viable workarounds for this issue other than rebooting the device and monitoring for the Indicator of Compromise (IoC). Once the condition is cleared from the log files - the absence of the error message indicates the condition has cleared - the device is not exploitable to the situation, and the actions taken which lead to the IoC being present should not be taken again, until a fixed release can be applied.

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 .