CVE-2024-21610: Junos OS: If in a scaled CoS scenario information on CoS state is gathered mgd processes get stuck

Severity: medium (CVSS 4.3 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.5% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2024-04-12 · updated 2026-06-17
Weakness: CWE-755

Description

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.

Affected products

Juniper Junos OS: before 20.4; 20.4, 20.4-r1, 20.4-r1-s1, 20.4-r2, 20.4-r2-s1, 20.4-r2-s2 (+87) — fixed in 20.4

How to fix

Upgrade to a fixed version: Juniper Junos OS 20.4. Check the vendor advisory for mitigations.

References

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