CVE-2026-1586 Overview
A denial of service vulnerability has been discovered in Open5GS, an open-source implementation of 5G Core and EPC (Evolved Packet Core). The flaw exists in the ogs_gtp2_f_teid_to_ip function within the /sgwc/s11-handler.c file of the SGWC (Serving Gateway Control Plane) component. This vulnerability allows remote attackers to cause service disruption through manipulation of GTP (GPRS Tunneling Protocol) traffic, potentially impacting 5G network availability.
Critical Impact
Remote attackers can exploit this vulnerability to disrupt 5G core network services, causing denial of service conditions that may affect mobile network subscribers and telecommunications infrastructure.
Affected Products
- Open5GS versions up to 2.7.5
- Open5GS SGWC (Serving Gateway Control Plane) component
- Systems running the affected s11-handler.c module
Discovery Timeline
- 2026-01-29 - CVE-2026-1586 published to NVD
- 2026-01-29 - Last updated in NVD database
Technical Details for CVE-2026-1586
Vulnerability Analysis
This vulnerability is classified under CWE-404 (Improper Resource Shutdown or Release), indicating that the affected function fails to properly handle resource management when processing specific inputs. The ogs_gtp2_f_teid_to_ip function in the SGWC's S11 interface handler does not adequately validate or manage resources during GTP-C (GPRS Tunneling Protocol - Control Plane) message processing.
The S11 interface is a critical control plane interface between the MME (Mobility Management Entity) and the SGW-C in 4G/5G networks. Improper handling of F-TEID (Fully Qualified Tunnel Endpoint Identifier) to IP conversion operations can lead to resource exhaustion or crash conditions, resulting in denial of service.
Root Cause
The root cause lies in improper resource handling within the ogs_gtp2_f_teid_to_ip function. When processing malformed or specially crafted GTP-C messages containing manipulated F-TEID information, the function fails to properly release allocated resources or handle error conditions, leading to resource depletion or component failure.
Attack Vector
This vulnerability can be exploited remotely over the network without requiring authentication or user interaction. An attacker with network access to the S11 interface can send specially crafted GTP-C messages to the SGWC component. The manipulation targets the F-TEID to IP address conversion process, which when exploited causes the SGWC to enter a denial of service state.
The attack does not require any privileges and can be initiated from any network position with access to the GTP-C control plane interface. According to the issue report, an exploit has been published and the vulnerability is confirmed as exploitable.
Detection Methods for CVE-2026-1586
Indicators of Compromise
- Unexpected crashes or restarts of the Open5GS SGWC process
- Abnormal GTP-C traffic patterns on the S11 interface
- Increased memory consumption or resource exhaustion in the SGWC component
- Service degradation or unavailability of the Serving Gateway Control Plane
Detection Strategies
- Monitor Open5GS SGWC process health and implement automated restart detection
- Deploy network intrusion detection rules to identify malformed GTP-C messages targeting the S11 interface
- Implement log analysis for error messages related to ogs_gtp2_f_teid_to_ip function failures
- Configure alerting for abnormal GTP protocol behavior or unexpected F-TEID values
Monitoring Recommendations
- Enable detailed logging for the SGWC component and S11 interface handler
- Implement real-time monitoring of Open5GS service availability and response times
- Deploy network traffic analysis tools to baseline and detect anomalous GTP-C traffic patterns
- Set up health checks and automated failover mechanisms for critical 5G core components
How to Mitigate CVE-2026-1586
Immediate Actions Required
- Update Open5GS to a patched version beyond 2.7.5 when available
- Review and restrict network access to the S11 interface to trusted MME nodes only
- Implement network segmentation to isolate GTP-C control plane traffic
- Enable rate limiting on GTP-C interfaces to mitigate potential DoS attacks
Patch Information
The issue has been reported as already-fixed according to the vulnerability disclosure. Administrators should monitor the Open5GS GitHub repository for official patch releases and upgrade instructions. The fix addresses the improper resource handling in the ogs_gtp2_f_teid_to_ip function within the SGWC S11 handler.
For additional technical details and discussion, refer to the VulDB advisory.
Workarounds
- Implement strict network access controls to limit S11 interface exposure to authorized network elements only
- Deploy a GTP firewall or deep packet inspection solution to filter malformed GTP-C messages
- Configure redundant SGWC instances with automatic failover to maintain service availability
- Enable enhanced monitoring and alerting to quickly detect and respond to exploitation attempts
# Configuration example - Network access restriction for S11 interface
# Add firewall rules to restrict S11 interface access (example using iptables)
iptables -A INPUT -p udp --dport 2123 -s <trusted_mme_ip> -j ACCEPT
iptables -A INPUT -p udp --dport 2123 -j DROP
# Enable verbose logging for SGWC component
# In open5gs configuration (sgwc.yaml), set logging level:
# logger:
# level: debug
# domain: sgwc
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
