CVE-2021-0244

Summary

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.

Affected Software

VendorProductVersion RangeStatus
Juniper NetworksJunos OS14.1X53 < 14.1X53-D49affected
Juniper NetworksJunos OS15.1 < 15.1R7-S6affected
Juniper NetworksJunos OS16.1 < 16.1R7-S7affected
Juniper NetworksJunos OS16.2 < 16.2R2-S11, 16.2R3affected
Juniper NetworksJunos OS17.1 < 17.1R2-S11, 17.1R3affected
Juniper NetworksJunos OS17.2 < 17.2R2-S8, 17.2R3-S3affected
Juniper NetworksJunos OS17.3 < 17.3R2-S5, 17.3R3-S7affected
Juniper NetworksJunos OS17.4 < 17.4R2-S9, 17.4R3affected
Juniper NetworksJunos OS18.1 < 18.1R3-S5affected
Juniper NetworksJunos OS18.2 < 18.2R2-S6, 18.2R3affected
Juniper NetworksJunos OS18.3 < 18.3R1-S7, 18.3R2-S3, 18.3R3affected
Juniper NetworksJunos OS18.4 < 18.4R1-S5, 18.4R2affected
Juniper NetworksJunos OS19.1 < 19.1R1-S4, 19.1R2affected
Juniper NetworksJunos OS15.1X49 < 15.1X49-D191, 15.1X49-D200affected

Weaknesses

  • 364 - Signal Handler Race Condition
  • Denial of Service (DoS)
  • Absence of a specific protection mechanism to avoid a race condition.

Workarounds

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.

ADP Enrichment

CVE Program Container

Additional References

References