Junos OS (SRX firewalls)
CVE-2024-21610: If in a scaled CoS scenario information on CoS state is gathered mgd processes get stuck
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).
Published
Automatic summary from the vendor's CVE record. We haven't written a full analysis of this vulnerability yet.
Affected and fixed versions
| Product / branch | Fixed in |
|---|---|
| Junos OS 0 | 20.4R3-S9 or later |
| Junos OS 21.2 | 21.2R3-S7 or later |
| Junos OS 21.3 | 21.3R3-S5 or later |
| Junos OS 21.4 | 21.4R3-S5 or later |
| Junos OS 22.1 | 22.1R3-S4 or later |
| Junos OS 22.2 | 22.2R3-S3 or later |
| Junos OS 22.3 | 22.3R3-S2 or later |
| Junos OS 22.4 | 22.4R3 or later |
| Junos OS 23.2 | 23.2R1-S2, 23.2R2 or later |
Always confirm against the vendor advisory, which lists every fixed hotfix.
What it is
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 extensive | match mgd | match sbwait
This issue affects Juniper Networks Junos OS: * All versions earlier than 20.4R3-S9; * 21.2 versions earlier than 21.2R3-S7; * 21.3 versions earlier than 21.3R3-S5; * 21.4 versions earlier than 21.4R3-S5; * 22.1 versions earlier than 22.1R3-S4; * 22.2 versions earlier than 22.2R3-S3; * 22.3 versions earlier than 22.3R3-S2; * 22.4 versions earlier than 22.4R3; * 23.2 versions earlier than 23.2R1-S2, 23.2R2.
Workarounds
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.
Exploitation
Juniper SIRT is not aware of any malicious exploitation of this vulnerability.
Sources
KEV status, EPSS score and vendor data refreshed automatically, last on 13 Oct 2026.