CVE-2026-44325
Analyzed Analyzed - Analysis Complete
Type Confusion in free5GC NRF SBI Token Handler

Publication date: 2026-05-27

Last updated on: 2026-05-28

Assigner: GitHub, Inc.

Description
free5GC is an open-source implementation of the 5G core network. Prior to 4.2.2, free5GC's NRF root SBI endpoint POST /oauth2/token contains a parser-level type-confusion bug family. The handler in NFs/nrf/internal/sbi/api_accesstoken.go reflects over models.NrfAccessTokenAccessTokenReq, special-cases only plain string and NrfNfManagementNfType fields, and treats every other field as if it were a single models.PlmnId. The parsed *models.PlmnId is then assigned with reflect.Value.Set() to whichever field name the attacker put in the form body, which panics whenever the destination field's real type is incompatible (slice, different struct, primitive). Gin recovery converts each panic into HTTP 500, but the endpoint remains remotely panicable from a single unauthenticated form-encoded request and is repeatedly triggerable. This vulnerability is fixed in 4.2.2.
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Meta Information
Published
2026-05-27
Last Modified
2026-05-28
Generated
2026-06-17
AI Q&A
2026-05-27
EPSS Evaluated
2026-06-15
NVD
CVE-2026-44325
EUVD
EUVD-2026-32573
Affected Vendors & Products
Showing 1 associated CPE
Vendor Product Version / Range
free5gc free5gc to 4.2.2 (exc)
Helpful Resources
Exploitability
CWE
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KEV
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CWE ID Description
CWE-20 The product receives input or data, but it does not validate or incorrectly validates that the input has the properties that are required to process the data safely and correctly.
CWE-755 The product does not handle or incorrectly handles an exceptional condition.
CWE-843 The product allocates or initializes a resource such as a pointer, object, or variable using one type, but it later accesses that resource using a type that is incompatible with the original type.
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Mitigation Strategies

The immediate mitigation step is to upgrade free5GC to version 4.2.2 or later, where this vulnerability has been fixed.

Until the upgrade can be performed, consider restricting access to the NRF root SBI endpoint /oauth2/token to trusted networks or applying firewall rules to block unauthenticated requests to this endpoint.

Compliance Impact

CVE-2026-44325 is a denial-of-service vulnerability in the free5GC NRF component that allows unauthenticated attackers to cause the service to panic and return HTTP 500 errors repeatedly. The primary impact is on availability, as the vulnerability can degrade or deny token issuance services.

There is no information in the provided context or resources indicating that this vulnerability leads to unauthorized access, data leakage, or modification of personal or sensitive data. Therefore, it does not directly affect confidentiality or integrity aspects that are critical for compliance with standards like GDPR or HIPAA.

However, the availability degradation caused by this vulnerability could indirectly impact compliance if the affected service is critical for meeting uptime or service availability requirements mandated by certain regulations or organizational policies.

In summary, this vulnerability primarily impacts availability and does not appear to directly violate data protection or privacy requirements under common standards such as GDPR or HIPAA.

Executive Summary

The vulnerability exists in free5GC, an open-source 5G core network implementation, specifically in the NRF root SBI endpoint POST /oauth2/token before version 4.2.2. It is a parser-level type-confusion bug where the handler incorrectly treats most fields as a single type (models.PlmnId) except for two special-cased fields. This causes a panic when the actual field type is incompatible, such as slices or different structs. An attacker can remotely trigger this panic repeatedly with unauthenticated form-encoded requests, causing the server to respond with HTTP 500 errors.

Impact Analysis

This vulnerability can cause denial of service (DoS) by repeatedly triggering panics in the server, leading to HTTP 500 errors. Since the endpoint is remotely accessible and unauthenticated, an attacker can exploit this to disrupt the availability of the free5GC network function, potentially impacting network reliability and service continuity.

Detection Guidance

This vulnerability can be detected by sending unauthenticated form-encoded POST requests to the free5GC NRF root SBI endpoint /oauth2/token and observing if the server responds with HTTP 500 errors due to panics triggered by type-confusion in the parser.

A possible detection method is to craft POST requests with specially crafted form data that includes fields with incompatible types to trigger the panic.

  • Use curl to send a POST request to the /oauth2/token endpoint with form data containing unexpected field types, for example: curl -X POST http://<free5gc-nrf-host>/oauth2/token -d 'unexpectedField[]=value'
  • Monitor the server responses for HTTP 500 status codes indicating a panic occurred.
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