An Improper Handling of Exceptional Conditions vulnerability in the Class of Service daemon (cosd) of Juniper Networks Junos OS allows an authenticated, network-based attacker with low privileges to cause a limited Denial of Service (DoS). In a scaled CoS scenario with 1000s of interfaces, when specific low privileged commands, received over NETCONF, SSH or telnet, are handled by cosd on behalf of mgd, the respective child management daemon (mgd) processes will get stuck. In case of (Netconf over) SSH this leads to stuck SSH sessions, so that when the connection-limit for SSH is reached, new sessions can't be established anymore. A similar behavior will be seen for telnet etc. Stuck mgd processes can be monitored by executing the following command: user@host> show system processes ext
The following software releases have been updated to resolve this specific issue: Junos OS: 20.4R3-S9, 21.2R3-S7, 21.3R3-S5, 21.4R3-S5, 22.1R3-S4, 22.2R3-S3, 22.3R3-S2, 22.4R3, 23.2R1-S2, 23.2R2, 23.4R1, and all subsequent releases.
While not a workaround, the number of stuck mgd processes can be monitored and once they reach a high level they can be proactively terminated.
| Product | Vulnerable range | Fixed version | Advisory |
|---|---|---|---|
| Juniper Networks Junos OS | <20.4R3-S9 | 20.4R3-S9 | advisory ↗ |
| Juniper Networks Junos OS | >=21.2<21.2R3-S7 | 21.2R3-S7 | advisory ↗ |
| Juniper Networks Junos OS | >=21.3<21.3R3-S5 | 21.3R3-S5 | advisory ↗ |
| Juniper Networks Junos OS | >=21.4<21.4R3-S5 | 21.4R3-S5 | advisory ↗ |
| Juniper Networks Junos OS | >=22.1<22.1R3-S4 | 22.1R3-S4 | advisory ↗ |
| Juniper Networks Junos OS | >=22.2<22.2R3-S3 | 22.2R3-S3 | advisory ↗ |
| Juniper Networks Junos OS | >=22.3<22.3R3-S2 | 22.3R3-S2 | advisory ↗ |
| Juniper Networks Junos OS | >=22.4<22.4R3 | 22.4R3 | advisory ↗ |
| Juniper Networks Junos OS | >=23.2<23.2R1-S2, 23.2R2 | 23.2R1-S2, 23.2R2 | advisory ↗ |