free5GC is an open-source implementation of the 5G core network. Prior to 4.2.2, free5GC's NEF mounts the nnef-callback route group without inbound OAuth2/bearer-token authorization. A forged or arbitrary bearer token (e.g. Authorization: Bearer not-a-real-token) is enough to reach the SMF-callback handler -- the callback body is parsed and dispatched into NEF business logic instead of being rejected at the auth boundary. Same root cause as the other NEF SBI findings: the route group is mounted without any inbound auth middleware. NEF does not authenticate the producer NF identity before processing callback content; if an attacker can guess or obtain a valid NotifId, this missing auth boundary lets forged callbacks act on real subscription state. The route group is also reachable even when the runtime ServiceList does not declare it (it lists only nnef-pfdmanagement and nnef-oam). This vulnerability is fixed in 4.2.2.

Project Subscriptions

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Advisories
Source ID Title
Github GHSA Github GHSA GHSA-wqfh-gq79-j8mf free5GC's NEF nnef-callback route group is unauthenticated; forged callback requests are accepted into the processing path
Fixes

Solution

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Workaround

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History

Wed, 27 May 2026 16:30:00 +0000

Type Values Removed Values Added
Description free5GC is an open-source implementation of the 5G core network. Prior to 4.2.2, free5GC's NEF mounts the nnef-callback route group without inbound OAuth2/bearer-token authorization. A forged or arbitrary bearer token (e.g. Authorization: Bearer not-a-real-token) is enough to reach the SMF-callback handler -- the callback body is parsed and dispatched into NEF business logic instead of being rejected at the auth boundary. Same root cause as the other NEF SBI findings: the route group is mounted without any inbound auth middleware. NEF does not authenticate the producer NF identity before processing callback content; if an attacker can guess or obtain a valid NotifId, this missing auth boundary lets forged callbacks act on real subscription state. The route group is also reachable even when the runtime ServiceList does not declare it (it lists only nnef-pfdmanagement and nnef-oam). This vulnerability is fixed in 4.2.2.
Title free5GC: NEF nnef-callback route group is unauthenticated; forged callback requests are accepted into the processing path
Weaknesses CWE-306
CWE-862
References
Metrics cvssV3_1

{'score': 7.3, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L'}


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cve-icon MITRE

Status: PUBLISHED

Assigner: GitHub_M

Published:

Updated: 2026-05-27T17:44:48.702Z

Reserved: 2026-05-05T19:00:06.022Z

Link: CVE-2026-44320

cve-icon Vulnrichment

No data.

cve-icon NVD

Status : Received

Published: 2026-05-27T17:16:37.177

Modified: 2026-05-27T17:16:37.177

Link: CVE-2026-44320

cve-icon Redhat

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cve-icon OpenCVE Enrichment

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Weaknesses