Improper Input Validation in free5gc Leads to DoS

Executive Summary

This vulnerability is a Denial of Service (DoS) issue in free5gc v4.0.1 caused by improper input validation in the HTTPModifySubscription handler. Attackers can exploit it by sending a crafted PATCH request with a short JSON path, triggering a 'slice bounds out of range' panic that crashes the AMF process.

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Detection Guidance

To detect this vulnerability, monitor for crashes in the free5GC AMF process or HTTPModifySubscription handler. Check logs for 'slice bounds out of range' errors or server panics. Use network traffic analysis tools like tcpdump or Wireshark to inspect incoming PATCH requests targeting the AMF event subscription endpoint for malformed paths shorter than 11 characters.

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Impact Analysis

This vulnerability allows attackers to crash the free5GC AMF service by sending a maliciously crafted request, causing a DoS. This disrupts network operations relying on the AMF component, potentially leading to service unavailability for users.

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Compliance Impact

This vulnerability primarily causes a Denial of Service (DoS) by crashing the free5GC AMF process, which could disrupt network availability. For compliance with standards like GDPR or HIPAA, such disruptions may impact data processing operations or service availability, potentially violating requirements for continuous access to critical systems. However, the provided context does not explicitly link this issue to specific compliance violations.

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Mitigation Strategies

Immediately upgrade free5GC to a patched version if available. If not, implement input validation in the HTTPModifySubscription handler to check path length before processing. Temporarily block or rate-limit PATCH requests to the vulnerable endpoint. Monitor AMF processes for crashes and restart them if they occur.

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