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Vulnerability record · CVE-2026-44320 · published 27 May 2026

CVE-2026-44320: Free5gc missing authentication for critical function vulnerability

Free5gc · Free5gc

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.

7.3 CVSS 3.1 High EPSS 0.38% · top 70.5% CWE-306 · Missing authentication for critical functionCWE-862 · Missing authorization
7.3CVSS 3.1 base score
0.38%EPSS exploitation probability, 30 days
NoNot in CISA KEV
1Affected product versions listed by NVD
4References, 3 tagged exploit
17 Jun 2026Last modified by NVD

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.

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L

Affected products

1 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
https://github.com/free5gc/free5gc/issues/860 ExploitIssue Tracking
https://github.com/free5gc/free5gc/security/advisories/GHSA-wqfh-gq79-j8mf ExploitVendor Advisory
https://github.com/free5gc/nef/pull/24 Issue TrackingPatch
https://github.com/free5gc/free5gc/security/advisories/GHSA-wqfh-gq79-j8mf ExploitVendor Advisory

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Related vulnerabilities

Same products first, then exploited flaws of the same weakness class.

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Source: NIST National Vulnerability Database (record CVE-2026-44320), CISA KEV, FIRST EPSS (scores of 2026-09-27). This page is refreshed as NVD updates the record.