Forged SMF callbacks via missing route authentication
Published May 27, 2026 · Updated May 27, 2026
Missing authentication in free5GC NEF before 4.2.2 allows remote attackers to submit forged SMF callbacks through the SBI. The nnef-callback route group lacks inbound OAuth2 middleware, so its API deserializes callback bodies and dispatches them by NotifId before authenticating the producer NF. Network reachability to the NEF SBI is required, and a valid NotifId lets an unauthenticated party alter real subscription state and downstream policy decisions.
Summary
What happened
Missing authentication in free5GC NEF before 4.2.2 allows remote attackers to submit forged SMF callbacks through the SBI. The nnef-callback route group lacks inbound OAuth2 middleware, so its API deserializes callback bodies and dispatches them by NotifId before authenticating the producer NF. Network reachability to the NEF SBI is required, and a valid NotifId lets an unauthenticated party alter real subscription state and downstream policy decisions.
The record
- CVE
- CVE-2026-44320
- Published
- May 27, 2026
- Updated
- May 27, 2026
- Vendor
- free5GC
- Product
- free5GC
- Classifications
- CWE-862, CWE-306, T1565.001
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- May 27, 2026CVE publishedPublication date reported by the CVE source.
- May 27, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=< 4.2.2
What conditions does exploitation require?
What is affected?
Published CVSS scores
CVSS describes severity. EPSS estimates exploitation probability.
Attacks
What attackers are doing with it
Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.
Weakness, pattern, technique
Public exploit references
- Forged NEF SMF callback proof of conceptproof of concept · demonstrated
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Technologies
Your stack
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Your stack
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