Executive Summary

This vulnerability exists in Open5GS up to version 2.7.7, specifically in the Network Slice Selection Function (NSSF) component. It occurs in the function ogs_sbi_discovery_option_add_service_names within the /lib/sbi/message.c library. When a GET request is made to the endpoint `/nnssf-nsselection/v2/network-slice-information` with an oversized `service-names` query parameter (exceeding the allowed number), the parser triggers an assertion failure. This causes the NSSF process to crash and terminate unexpectedly.

The root cause is that the parser does not properly handle requests with too many service names, leading to a denial of service through process termination instead of gracefully handling the error.

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Impact Analysis

This vulnerability can cause a denial of service (DoS) by crashing the NSSF component of Open5GS when it receives a specially crafted request with too many service names. Since the NSSF process terminates unexpectedly, it can disrupt network slice selection services, potentially affecting the availability and reliability of the affected system.

Because the attack can be performed remotely by sending a malicious GET request, it poses a risk of service interruption without requiring local access.

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Detection Guidance

This vulnerability can be detected by monitoring for crashes or unexpected termination of the NSSF process in Open5GS when it processes specific HTTP GET requests.

Specifically, sending a GET request to the endpoint `/nnssf-nsselection/v2/network-slice-information` with an oversized `service-names` query parameter (e.g., 80 service names) can trigger the vulnerability and cause the NSSF to crash.

• Use a command like curl to send a crafted request: curl -v "http://<open5gs-nssf-ip>:<port>/nnssf-nsselection/v2/network-slice-information?service-names=name1,name2,...,name80"
• Monitor the NSSF process logs or system logs for exit code 139 or assertion failures indicating a crash.

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Mitigation Strategies

Immediate mitigation steps include restricting or filtering incoming requests to the NSSF component to prevent oversized `service-names` query parameters.

Implement network-level protections such as firewall rules or API gateways to block or limit requests with excessive query parameters targeting the vulnerable endpoint.

Monitor the NSSF process for crashes and consider restarting it automatically if it terminates unexpectedly.

Since the project has not yet responded with a fix, stay updated on official patches or updates from Open5GS and apply them once available.

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Compliance Impact

The provided information does not specify any direct impact of this vulnerability on compliance with common standards and regulations such as GDPR or HIPAA.

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