CVE-2026-2523 Overview
A vulnerability has been identified in Open5GS up to version 2.7.6 affecting the Session Management Function (SMF) component. The vulnerability exists in the function smf_gn_handle_create_pdp_context_request within the file /src/smf/gn-handler.c. This flaw allows remote attackers to trigger a reachable assertion, leading to a denial of service condition in the 5G core network infrastructure.
Critical Impact
Remote attackers can exploit this vulnerability to crash the SMF component in Open5GS deployments, potentially disrupting 5G network services and session management for connected devices.
Affected Products
- Open5GS versions up to 2.7.6
- Open5GS SMF (Session Management Function) component
- Systems running Open5GS with GTPv1-C/GTPv2-C protocol handling enabled
Discovery Timeline
- 2026-02-16 - CVE CVE-2026-2523 published to NVD
- 2026-02-18 - Last updated in NVD database
Technical Details for CVE-2026-2523
Vulnerability Analysis
This vulnerability is classified as CWE-617 (Reachable Assertion), which occurs when the application contains an assertion that can be triggered by an attacker. In the context of Open5GS, the vulnerable function smf_gn_handle_create_pdp_context_request processes incoming PDP (Packet Data Protocol) context creation requests. When specially crafted input is provided, the assertion condition is met, causing the SMF process to terminate unexpectedly.
The exploit has been made public and may be actively used against vulnerable Open5GS deployments. The Open5GS project was notified through a GitHub issue report but has not yet responded to the disclosure.
Root Cause
The root cause lies in insufficient input validation within the smf_gn_handle_create_pdp_context_request function. When processing GTPv1-C Create PDP Context Request messages, the code contains an assertion that can be triggered by malformed or unexpected input parameters. Assertions are typically used during development to catch programming errors, but when left in production code and reachable via external input, they become a denial of service vector.
Attack Vector
The vulnerability can be exploited remotely over the network without authentication. An attacker with network access to the SMF's GTP-C interface can send maliciously crafted PDP context creation requests. When the vulnerable function processes these requests, the assertion is triggered, causing the SMF process to crash.
The attack does not require any user interaction or special privileges, making it particularly dangerous for exposed Open5GS deployments. While the attack does not directly compromise confidentiality or integrity, the availability impact on 5G core network services can be significant.
Detection Methods for CVE-2026-2523
Indicators of Compromise
- Unexpected SMF process crashes or restarts in Open5GS deployments
- Core dump files indicating assertion failures in gn-handler.c
- Unusual patterns of GTP-C Create PDP Context Request messages from external sources
- Service disruptions affecting subscriber session management
Detection Strategies
- Monitor Open5GS SMF process status and implement alerting for unexpected terminations
- Analyze GTP-C protocol traffic for malformed or anomalous PDP context creation requests
- Review system logs for assertion failure messages originating from /src/smf/gn-handler.c
- Deploy network intrusion detection rules targeting suspicious GTP-C traffic patterns
Monitoring Recommendations
- Implement process monitoring and automatic restart mechanisms for the SMF component
- Configure centralized logging to capture SMF crash events and associated network traffic
- Monitor GTP-C interface traffic volumes for anomalies that may indicate exploitation attempts
- Establish baseline metrics for normal SMF operation to detect deviation patterns
How to Mitigate CVE-2026-2523
Immediate Actions Required
- Review Open5GS deployment exposure and limit GTP-C interface access to trusted network segments only
- Implement network segmentation to restrict access to the SMF component from untrusted networks
- Deploy rate limiting on GTP-C interfaces to reduce the impact of potential exploitation attempts
- Monitor the Open5GS GitHub repository for security patches addressing this vulnerability
Patch Information
As of the last update, no official patch has been released by the Open5GS project. The vulnerability was reported through GitHub Issue #4285, but the project maintainers have not yet responded. Organizations using Open5GS should monitor the official repository for updates and apply patches as soon as they become available.
Workarounds
- Restrict network access to the SMF's GTP-C interface using firewall rules to allow only trusted peer connections
- Deploy a reverse proxy or GTP gateway with input validation capabilities in front of the SMF component
- Implement process supervision to automatically restart the SMF if it crashes due to exploitation
- Consider deploying Open5GS in a containerized environment with orchestration for rapid recovery
# Example: Restrict GTP-C interface access using iptables
# Allow only trusted GTP peers (replace with actual peer IPs)
iptables -A INPUT -p udp --dport 2123 -s 10.0.0.0/24 -j ACCEPT
iptables -A INPUT -p udp --dport 2123 -j DROP
# Enable process monitoring for SMF
systemctl enable open5gs-smfd
systemctl start open5gs-smfd
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
