CVE-2026-1586: Open5GS SGWC Denial of Service Vulnerability

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

bash

# 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