CVE-2024-39562 Junos OS Evolved: A high rate of SSH connections causes a Denial of Service
An unauthenticated attacker can cause a Denial of Service by flooding SSH connections, crashing xinetd and blocking legitimate SSH access on Junos OS Evolved devices.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2024-39562?
CVE-2024-39562 is a high-severity denial of service vulnerability in Juniper Junos Os Evolved, published on 10 Jul 2024. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
A Missing Release of Resource after Effective Lifetime vulnerability the xinetd process, responsible for spawning SSH daemon (sshd) instances, of Juniper Networks Junos OS Evolved allows an unauthenticated network-based attacker to cause a Denial of Service (DoS) by blocking SSH access for legitimate users. Continued receipt of these connections will create a sustained Denial of Service (DoS) condition.
The issue is triggered when a high rate of concurrent SSH requests are received and terminated in a specific way, causing xinetd to crash, and leaving defunct sshd processes. Successful exploitation of this vulnerability blocks both SSH access as well as services which rely upon SSH, such as SFTP, and Netconf over SSH.
Once the system is in this state, legitimate users will be unable to SSH to the device until service is manually restored. See WORKAROUND section below.
Administrators can monitor an increase in defunct sshd processes by utilizing the CLI command:
> show system processes | match sshd root 25219 30901 0 Jul16 ? 00:00:00 [sshd] <defunct>
This issue affects Juniper Networks Junos OS Evolved: * All versions prior to 21.4R3-S7-EVO * 22.3-EVO versions prior to 22.3R2-S2-EVO, 22.3R3-S2-EVO; * 22.4-EVO versions prior to 22.4R3-EVO; * 23.2-EVO versions prior to 23.2R2-EVO.
This issue does not affect Juniper Networks Junos OS Evolved 22.1-EVO nor 22.2-EVO.
Weakness: CWE-772
Which versions are affected by CVE-2024-39562?
It affects 1 product.
Products include Juniper Junos Os Evolved.
How do I fix CVE-2024-39562?
No fix has been published for CVE-2024-39562 yet. Limit exposure of the affected software until one is available.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2024-39562 being exploited?
There is no known exploitation of CVE-2024-39562 in the wild and no public exploit code.
Other vulnerabilities in Juniper Junos Os Evolved
- CVE-2026-21902 Junos OS Evolved: PTX Series: A vulnerability allows a unauthenticated, network-based attacker to execute code as root
- CVE-2023-28983 Junos OS Evolved: Shell Injection vulnerability in the gNOI server
- CVE-2025-21599 Denial of service in Junos OS Evolved
- CVE-2024-47502 Junos OS Evolved: TCP session state is not always cleared on the Routing Engine leading to DoS
- CVE-2024-39531 Junos OS Evolved: ACX 7000 Series: Protocol specific DDoS configuration affects other protocols
Sources
Also known as GHSA-8j3v-w6gq-fj6q.