Junos OS Evolved xinetd resource leak causing SSH DoS (before 22.3R2)
CVE-2024-39562 Published on July 10, 2024
Junos OS Evolved: A high rate of SSH connections causes a Denial of Service
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.
Vulnerability Analysis
CVE-2024-39562 is exploitable with network access, and does not require authorization privileges or user interaction. This vulnerability is considered to have a low attack complexity. The potential impact of an exploit of this vulnerability is considered to have no impact on confidentiality and integrity, and a high impact on availability.
Timeline
Initial Publication
Weakness Type
Missing Release of Resource after Effective Lifetime
The software does not release a resource after its effective lifetime has ended, i.e., after the resource is no longer needed. When a resource is not released after use, it can allow attackers to cause a denial of service by causing the allocation of resources without triggering their release. Frequently-affected resources include memory, CPU, disk space, power or battery, etc.
Products Associated with CVE-2024-39562
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Affected Versions
Juniper Networks Junos OS Evolved:- Before 21.4R3-S7-EVO is affected.
- Version 22.3-EVO and below 22.3R2-S2-EVO, 22.3R3-S2-EVO is affected.
- Version 22.4-EVO and below 22.4R3-EVO is affected.
- Version 23.2-EVO and below 23.2R2-EVO is affected.
- Version 22.1-EVO and below 22.1* is unaffected.
- Version 22.2-EVO and below 22.2* is unaffected.
- Before 21.4r3-s7 is affected.
- Version 22.3 and below 22.3r2-s2 is affected.
- Version 22.3 and below 22.3r3-s2 is affected.
- Version 22.4 and below 22.4r3 is affected.
- Version 23.2 and below 23.2r2 is affected.
Exploit Probability
EPSS (Exploit Prediction Scoring System) scores estimate the probability that a vulnerability will be exploited in the wild within the next 30 days. The percentile shows you how this score compares to all other vulnerabilities.