Vulnerabilities > CVE-2021-0244 - Race Condition vulnerability in Juniper Junos
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.
Vulnerable Configurations
| Part | Description | Count |
|---|---|---|
| OS | 246 | |
| Hardware | Juniper
| 22 |
Common Weakness Enumeration (CWE)
Common Attack Pattern Enumeration and Classification (CAPEC)
- Leveraging Race Conditions This attack targets a race condition occurring when multiple processes access and manipulate the same resource concurrently and the outcome of the execution depends on the particular order in which the access takes place. The attacker can leverage a race condition by "running the race", modifying the resource and modifying the normal execution flow. For instance a race condition can occur while accessing a file, the attacker can trick the system by replacing the original file with his version and cause the system to read the malicious file.
- Leveraging Time-of-Check and Time-of-Use (TOCTOU) Race Conditions This attack targets a race condition occurring between the time of check (state) for a resource and the time of use of a resource. The typical example is the file access. The attacker can leverage a file access race condition by "running the race", meaning that he would modify the resource between the first time the target program accesses the file and the time the target program uses the file. During that period of time, the attacker could do something such as replace the file and cause an escalation of privilege.