CVE-2025-59964 Overview
A Use of Uninitialized Resource vulnerability (CWE-908) has been identified in the Packet Forwarding Engine (PFE) of Juniper Networks Junos OS running on SRX4700 devices. This vulnerability allows an unauthenticated, network-based attacker to cause a Denial of Service (DoS) condition by sending any traffic destined to the Routing Engine (RE) when forwarding-options sampling is enabled.
The vulnerability is triggered when the PFE line card processes traffic destined for the Routing Engine, causing an FPC (Flexible PIC Concentrator) crash and restart. Continued receipt of such traffic can create a sustained DoS condition affecting the PFE line card, disrupting critical network operations. This issue affects both IPv4 and IPv6 traffic.
Critical Impact
Unauthenticated network attackers can crash and restart the FPC on SRX4700 devices, causing service disruption. Sustained attacks can maintain a persistent DoS condition against the Packet Forwarding Engine.
Affected Products
- Juniper Junos OS on SRX4700 devices
- Junos OS version 24.4 before 24.4R1-S3
- Junos OS version 24.4R2
Discovery Timeline
- 2025-10-09 - CVE CVE-2025-59964 published to NVD
- 2026-01-23 - Last updated in NVD database
Technical Details for CVE-2025-59964
Vulnerability Analysis
This vulnerability stems from the improper handling of uninitialized resources within the Packet Forwarding Engine when the forwarding-options sampling feature is enabled. The PFE, which is responsible for processing and forwarding network packets at high speed, fails to properly initialize critical resources before use when handling traffic destined to the Routing Engine.
The attack can be executed by any unauthenticated attacker with network access to the vulnerable device. No special privileges or user interaction are required to exploit this vulnerability. When triggered, the FPC component crashes and automatically restarts, temporarily disrupting all packet forwarding operations on the affected line card. An attacker who continues to send malicious traffic can maintain a persistent denial of service state.
The vulnerability specifically affects the SRX4700 series, which are high-performance security devices commonly deployed in enterprise and service provider edge environments. The impact extends beyond availability, as downstream systems relying on the SRX4700 for security services may also experience service degradation.
Root Cause
The root cause is a Use of Uninitialized Resource condition (CWE-908) in the Packet Forwarding Engine code path. When forwarding-options sampling is configured, the PFE attempts to access memory or data structures that have not been properly initialized during the processing of RE-destined traffic. This results in undefined behavior leading to an FPC crash.
The forwarding-options sampling feature is used for traffic monitoring, flow analysis, and collecting statistics about network traffic patterns. When enabled, it appears to introduce a code path where certain resources are accessed before initialization, creating the vulnerable condition.
Attack Vector
The attack vector is network-based and requires no authentication. An attacker can exploit this vulnerability by sending network traffic to the device that is destined for processing by the Routing Engine. This includes management traffic, routing protocol packets, or any other traffic that would normally be handled by the RE rather than forwarded through the device.
The vulnerability conditions that must be met are:
- Target device must be a Juniper SRX4700 running an affected Junos OS version
- Forwarding-options sampling must be enabled in the device configuration
- Attacker must have network connectivity to send traffic to the device
The attack does not require crafted packets or exploit payloads—any legitimate traffic destined to the RE can trigger the crash condition.
Detection Methods for CVE-2025-59964
Indicators of Compromise
- Repeated FPC crash and restart events in system logs
- Unexpected fpc process restarts visible in show chassis fpc output
- Core dump files generated during FPC crashes
- Intermittent packet loss or service disruption correlated with traffic spikes
Detection Strategies
- Monitor system logs for FPC crash events and restart cycles using syslog monitoring
- Implement SNMP traps for chassis component failures and FPC status changes
- Analyze core dump files to identify crash patterns consistent with this vulnerability
- Review device uptime and restart counters for abnormal patterns
Monitoring Recommendations
- Configure centralized logging to capture all chassis and PFE-related events
- Set up alerts for FPC restart events exceeding normal operational thresholds
- Monitor traffic patterns for unusual volumes of management or routing protocol traffic
- Implement network flow analysis to identify potential attack traffic targeting device management interfaces
How to Mitigate CVE-2025-59964
Immediate Actions Required
- Verify if forwarding-options sampling is enabled on SRX4700 devices running affected Junos OS versions
- Review the Juniper Support Advisory JSA103153 for specific guidance
- Plan upgrade to Junos OS version 24.4R1-S3 or 24.4R2 or later
- Implement access control lists to restrict traffic to device management interfaces
Patch Information
Juniper Networks has released patched versions of Junos OS that address this vulnerability. Organizations should upgrade to:
- Junos OS 24.4R1-S3 or later
- Junos OS 24.4R2 or later
For detailed patching instructions and download links, refer to the Juniper Support Advisory JSA103153. Additionally, the Juniper CLI Reference Guide provides documentation on the forwarding-options sampling configuration.
Workarounds
- Disable forwarding-options sampling feature if not operationally required until patching can be completed
- Implement firewall filters to restrict management traffic sources to trusted IP addresses
- Deploy rate limiting on management interfaces to mitigate sustained attack attempts
- Consider out-of-band management networks to reduce exposure of the Routing Engine to untrusted traffic
# Configuration example - Disabling forwarding-options sampling as workaround
# WARNING: Review operational impact before disabling sampling
delete forwarding-options sampling
commit
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
