CVE-2026-26025 Overview
CVE-2026-26025 is a Null Pointer Dereference vulnerability affecting free5GC SMF (Session Management Function), an open-source project providing 5th generation (5G) mobile core network functionality. The vulnerability allows an unauthenticated remote attacker to cause a denial of service condition by sending a malformed PFCP SessionReportRequest to the PFCP interface on UDP port 8805.
When the SMF component processes a specially crafted malformed PFCP SessionReportRequest message, it triggers a panic condition that terminates the entire SMF process. This vulnerability is particularly concerning in 5G network infrastructure where SMF availability is critical for session management operations.
Critical Impact
Remote attackers can crash the free5GC SMF service by sending malformed PFCP messages, causing denial of service to the 5G core network session management functionality.
Affected Products
- free5gc smf versions up to and including 1.4.1
Discovery Timeline
- 2026-02-24 - CVE CVE-2026-26025 published to NVD
- 2026-02-25 - Last updated in NVD database
Technical Details for CVE-2026-26025
Vulnerability Analysis
This vulnerability stems from improper handling of malformed PFCP (Packet Forwarding Control Protocol) messages within the free5GC SMF component. PFCP is a critical protocol used in 5G networks for communication between the Session Management Function (SMF) and the User Plane Function (UPF).
When the SMF receives a SessionReportRequest message on the PFCP interface (UDP/8805) that contains malformed or unexpected data structures, the Go-based application fails to properly validate the input before processing. This leads to a null pointer dereference condition (CWE-476) when the code attempts to access memory through an invalid or null reference.
The vulnerability can be exploited remotely over the network without requiring authentication or user interaction, making it accessible to attackers who can reach the PFCP interface.
Root Cause
The root cause is a Null Pointer Dereference (CWE-476) in the PFCP message handling code. The SMF component lacks proper input validation and error handling when parsing PFCP SessionReportRequest messages. When malformed data is received, the parsing logic may set pointers to null or invalid states, and subsequent code paths attempt to dereference these pointers without checking for validity. In Go, this manifests as a panic that, without proper recovery mechanisms, terminates the entire process.
Attack Vector
An attacker can exploit this vulnerability by sending crafted malformed PFCP SessionReportRequest messages to the SMF's PFCP interface on UDP port 8805. The attack is network-based and does not require any authentication or privileges. The attacker only needs network access to the PFCP interface, which in production environments may be reachable from UPF components or, in misconfigured deployments, from broader network segments.
The attack flow involves:
- Identifying a free5GC SMF instance with an accessible PFCP interface on UDP/8805
- Crafting a malformed PFCP SessionReportRequest message with invalid or missing required fields
- Sending the malformed message to the SMF
- The SMF attempts to process the message, encounters a null pointer, panics, and terminates
Technical details regarding the specific malformed message structure can be found in the GitHub Issue Discussion.
Detection Methods for CVE-2026-26025
Indicators of Compromise
- Unexpected SMF process termination or panic events in system logs
- SMF service becoming unavailable without scheduled maintenance
- Suspicious or malformed PFCP traffic on UDP port 8805 from untrusted IP addresses
- Repeated SMF restart events in a short time period indicating potential exploitation attempts
Detection Strategies
- Monitor PFCP interface traffic for malformed or anomalous SessionReportRequest messages
- Implement alerting on SMF process crashes or panic events in application logs
- Deploy network intrusion detection signatures for malformed PFCP protocol messages
- Review system logs for Go panic stack traces originating from PFCP handler functions
Monitoring Recommendations
- Enable detailed logging for PFCP message processing in the SMF component
- Configure process monitoring to alert on SMF service crashes with automatic restart
- Implement network flow monitoring for UDP/8805 traffic to detect unusual patterns
- Set up log aggregation to correlate SMF panic events with incoming PFCP traffic sources
How to Mitigate CVE-2026-26025
Immediate Actions Required
- Apply ACL/firewall rules to restrict PFCP interface (UDP/8805) access to only trusted UPF IP addresses
- Configure network edge devices to drop or inspect malformed PFCP SessionReportRequest messages where feasible
- Implement process restart automation to minimize service downtime if exploitation occurs
- Review network architecture to ensure PFCP interface is not exposed to untrusted networks
Patch Information
No official upstream fix is currently available from the free5GC project for versions up to and including 1.4.1. Organizations should monitor the GitHub Security Advisory for updates on a patch release. In the interim, the workarounds described below should be implemented to reduce the attack surface.
Workarounds
- Configure firewall rules to restrict PFCP interface access to trusted UPF IP addresses only, significantly reducing the spoofing and abuse surface
- Deploy network edge inspection to drop malformed PFCP SessionReportRequest messages before they reach the SMF
- Add recover() handling around PFCP handler dispatch in the SMF code to prevent whole-process termination (code-level mitigation requiring local modification)
- Implement network segmentation to isolate PFCP interfaces from untrusted network segments
# Example iptables rules to restrict PFCP interface access
# Replace TRUSTED_UPF_IP with your actual UPF IP addresses
# Allow PFCP traffic only from trusted UPF
iptables -A INPUT -p udp --dport 8805 -s TRUSTED_UPF_IP -j ACCEPT
# Drop all other PFCP traffic
iptables -A INPUT -p udp --dport 8805 -j DROP
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
