CVE-2021-0244

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.

• CWE-362

• https://kb.juniper.net/JSA11137Vendor Advisory
• https://kb.juniper.net/JSA11137Vendor Advisory

Published

Apr 22, 2021

Last Modified

Jun 17, 2026

Status

Modified

• How Strix found a critical auth bypass in etcdStrix autonomously discovered a critical authentication bypass in etcd, later designated CVE-2026-33413.
• Autonomous PentestingAI agents that find and validate exploitable vulnerabilities like this one across your applications.
• PR ReviewsPentest every pull request so vulnerable code is caught before it ships to production.
• AI Penetration TestingHow AI-driven penetration testing continuously covers your attack surface.

• CVE-2021-0238When a MX Series is configured as a Broadband Network Gatewa…5.5
• CVE-2021-0239In Juniper Networks Junos OS Evolved, receipt of a stream of…6.5
• CVE-2021-0240On Juniper Networks Junos OS platforms configured as DHCPv6 …6.5
• CVE-2021-0241On Juniper Networks Junos OS platforms configured as DHCPv6 …6.5
• CVE-2021-0242A vulnerability due to the improper handling of direct memor…6.5
• CVE-2021-0243Improper Handling of Unexpected Data in the firewall policer…4.7
• CVE-2021-0245A Use of Hard-coded Credentials vulnerability in Juniper Net…7.8
• CVE-2021-0246On SRX1500, SRX4100, SRX4200, SRX4600, SRX5000 Series with S…7.3
• CVE-2021-0247A Race Condition (Concurrent Execution using Shared Resource…5.5
• CVE-2021-0248This issue is not applicable to NFX NextGen Software. On NFX…10
• CVE-2021-0249On SRX Series devices configured with UTM services a buffer …9.8
• CVE-2021-0250In segment routing traffic engineering (SRTE) environments w…7.5