CVE-2025-21596 in Junos OS
Summary
by MITRE • 01/09/2025
An Improper Handling of Exceptional Conditions vulnerability in the command-line processing of Juniper Networks Junos OS on SRX1500, SRX4100, and SRX4200 devices allows a local, low-privileged authenticated attacker executing the 'show chassis environment pem' command to cause the chassis daemon (chassisd) to crash and restart, resulting in a temporary Denial of Service (DoS). However, repeated execution of this command will eventually cause the chassisd process to fail to restart, impacting packet processing on the system.
This issue affects Junos OS on SRX1500, SRX4100, SRX4200:
* All versions before 21.4R3-S9, * from 22.2 before 22.2R3-S5, * from 22.3 before 22.3R3-S4, * from 22.4 before 22.4R3-S4, * from 23.2 before 23.2R2-S3, * from 23.4 before 23.4R2-S1.
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Analysis
by VulDB Data Team • 04/29/2026
This vulnerability represents a critical weakness in the exception handling mechanisms of Juniper Networks Junos OS affecting specific SRX series devices including SRX1500, SRX4100, and SRX4200 platforms. The flaw manifests in the command-line processing subsystem where the 'show chassis environment pem' command fails to properly manage exceptional conditions during execution. This improper handling creates a scenario where legitimate administrative commands can trigger unexpected system behavior leading to service disruption. The vulnerability specifically targets the chassis daemon process known as chassisd which is responsible for managing hardware environment monitoring and system health reporting functions within the SRX platform architecture.
The technical exploitation of this vulnerability occurs through a local authenticated attack vector where a low-privileged user with access to the command-line interface can execute the targeted command repeatedly. Each execution causes the chassisd process to crash and restart, creating a temporary denial of service condition that disrupts the normal operation of hardware environmental monitoring. The vulnerability classification aligns with CWE-703, Improper Handling of Exceptional Conditions, which describes situations where programs fail to properly handle exceptional circumstances during execution. This weakness creates a cascading effect where repeated exploitation eventually leads to complete process failure rather than just temporary disruption.
From an operational impact perspective, this vulnerability creates significant reliability concerns for network infrastructure devices that depend on continuous hardware monitoring capabilities. The chassisd daemon failure affects packet processing capabilities on the system since the chassis daemon is integral to maintaining system stability and hardware status reporting. When the process fails to restart properly after repeated crashes, the entire system experiences a more severe disruption that impacts network traffic flow and monitoring capabilities. This behavior demonstrates how seemingly minor exception handling flaws can compound into major system reliability issues that affect core network functionality and availability.
The vulnerability affects multiple software version ranges across different Junos OS release branches, indicating this is not an isolated incident but rather a persistent issue in the codebase that spans several major releases. The affected versions include all releases before 21.4R3-S9, and various branches from 22.2 through 23.4 that have not yet received the necessary patches. This widespread impact suggests that the underlying code pattern causing the exception handling failure is present across multiple code versions, making the vulnerability particularly concerning for organizations maintaining multiple device types and software versions. Organizations should prioritize patching efforts across all affected versions to prevent potential exploitation that could impact network availability and security monitoring capabilities. The ATT&CK framework categorizes this vulnerability under T1499.004, Network Denial of Service, and T1562.001, Impairing Availability, as it directly impacts system availability through process crashes and restart failures that ultimately compromise network infrastructure reliability.