CVE-2026-30653: Free5gc DoS Vulnerability

CVE-2026-30653 Overview

A Denial of Service vulnerability exists in Free5GC v.4.2.0 and earlier versions that allows a remote attacker to disrupt 5G core network operations. The vulnerability is located in the HandleAuthenticationFailure function within the Access and Mobility Management Function (AMF) component. An unauthenticated remote attacker can exploit this flaw to cause service disruption, potentially affecting mobile network subscribers relying on the Free5GC infrastructure.

Critical Impact

Remote attackers can exploit this vulnerability to cause denial of service in 5G core network deployments using Free5GC, disrupting authentication services and potentially affecting all connected mobile devices.

Affected Products

• Free5GC v.4.2.0 and earlier versions
• Free5GC AMF (Access and Mobility Management Function) component
• 5G core network deployments utilizing vulnerable Free5GC versions

Discovery Timeline

• 2026-03-24 - CVE-2026-30653 published to NVD
• 2026-03-24 - Last updated in NVD database

Technical Details for CVE-2026-30653

Vulnerability Analysis

This vulnerability affects the Access and Mobility Management Function (AMF) component of Free5GC, an open-source 5G core network implementation. The AMF is a critical network function responsible for handling UE (User Equipment) registration, connection management, and authentication procedures in 5G networks.

The flaw exists in the HandleAuthenticationFailure function, which processes authentication failure events during the 5G-AKA (Authentication and Key Agreement) procedure. When this function receives specially crafted or malformed authentication failure messages, it fails to properly handle the error condition, leading to resource exhaustion or service crash.

The vulnerability is classified under CWE-400 (Uncontrolled Resource Consumption), indicating that the affected function does not properly limit resource allocation when processing authentication failure events. This allows an attacker to send a flood of malicious authentication failure messages, consuming server resources and ultimately causing the AMF service to become unresponsive.

Root Cause

The root cause lies in improper input validation and resource management within the HandleAuthenticationFailure function. The function does not implement adequate rate limiting or validation checks when processing authentication failure messages, allowing attackers to exhaust system resources through repeated malicious requests. This is characteristic of CWE-400 vulnerabilities where resource consumption is not properly controlled.

Attack Vector

The attack can be executed remotely over the network without requiring any authentication or user interaction. An attacker with network access to the Free5GC AMF interface can send crafted authentication failure messages to trigger the vulnerability.

The attack scenario involves:

1. Attacker identifies a Free5GC deployment with an exposed AMF component
2. Attacker sends malformed or repeated authentication failure messages to the HandleAuthenticationFailure endpoint
3. The AMF fails to properly handle these requests, leading to resource exhaustion
4. The AMF service becomes unavailable, disrupting 5G authentication services for legitimate users

This network-based attack requires no privileges or user interaction, making it particularly dangerous for exposed 5G core network deployments. For technical details regarding the specific exploitation mechanism, refer to the GitHub Issue Discussion.

Detection Methods for CVE-2026-30653

Indicators of Compromise

• Unusual spike in authentication failure messages directed at the AMF component
• AMF service crashes or unexpected restarts in Free5GC deployments
• High CPU or memory utilization on servers running Free5GC AMF
• Increased network traffic targeting AMF authentication endpoints

Detection Strategies

• Monitor Free5GC AMF logs for abnormal volumes of authentication failure events
• Implement network intrusion detection rules to identify anomalous authentication traffic patterns
• Set up alerting for AMF service availability and resource utilization thresholds
• Deploy application-layer monitoring to track HandleAuthenticationFailure function invocations

Monitoring Recommendations

• Configure real-time monitoring for Free5GC AMF service health and availability
• Establish baseline metrics for normal authentication failure rates and alert on significant deviations
• Implement centralized logging for all 5G core network components with correlation capabilities
• Monitor network traffic at ingress points for volumetric attacks targeting authentication services

How to Mitigate CVE-2026-30653

Immediate Actions Required

• Identify all Free5GC deployments running version 4.2.0 or earlier in your environment
• Restrict network access to AMF interfaces to trusted sources only using firewall rules
• Implement rate limiting on authentication-related endpoints at the network perimeter
• Monitor affected systems for signs of exploitation while preparing for patching

Patch Information

Review the GitHub Issue Discussion for the latest information regarding patches and fixes from the Free5GC project. Organizations should monitor the Free5GC GitHub repository for updated releases that address this vulnerability and apply patches as soon as they become available.

Workarounds

• Deploy a reverse proxy or API gateway in front of the AMF component to implement rate limiting on authentication failure requests
• Configure network segmentation to isolate 5G core network components from untrusted network segments
• Implement IP-based access controls to restrict AMF interface access to known legitimate UE gateways and network functions
• Enable enhanced logging and monitoring to detect exploitation attempts while awaiting an official patch

# Example: Configure firewall rules to restrict AMF access (adjust ports/IPs as needed)
# Block external access to AMF interfaces
iptables -A INPUT -p tcp --dport 38412 -s 0.0.0.0/0 -j DROP
iptables -A INPUT -p tcp --dport 38412 -s 10.0.0.0/8 -j ACCEPT

# Enable rate limiting for SCTP connections to AMF
iptables -A INPUT -p sctp --dport 38412 -m limit --limit 100/second --limit-burst 200 -j ACCEPT
iptables -A INPUT -p sctp --dport 38412 -j DROP