What’s Vulnerable › Vulnerabilities

CVE-2026-44321: free5GC: SMF UPI POST /upi/v1/upNodesLinks exits the SMF process on overlapping UE pools (unauthenticated, reachable Fatalf)

• Severity: high (CVSS 7.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.4% probability of exploitation in the next 30 days
• Public exploit or detection template: yes
• Published: 2026-05-27 · updated 2026-10-14
• Weakness: CWE-306

Description

free5GC is an open-source implementation of the 5G core network. Prior to 4.2.2, free5GC's SMF mounts the UPI management route group without inbound OAuth2 middleware. The POST /upi/v1/upNodesLinks create-or-update handler accepts attacker-controlled JSON and passes it directly into UpNodesFromConfiguration(), which calls logger.InitLog.Fatalf(...) on several validation failures. One confirmed path is the UE-IP-pool overlap check: a single unauthenticated POST that adds a new UPF whose pool overlaps an existing UPF terminates the entire SMF process (docker ps shows Exited (1)), not just the goroutine. This vulnerability is fixed in 4.2.2.

Affected products

• free5gc: before 4.2.2 — fixed in 4.2.2

How to fix

Upgrade to a fixed version: free5gc 4.2.2. Check the vendor advisory for mitigations.

References

• https://github.com/free5gc/free5gc/issues/906
• https://github.com/free5gc/free5gc/security/advisories/GHSA-44qj-cghf-9p97
• https://github.com/free5gc/smf/commit/e0974e07ddab44a67d36a563cca383b2449e33e5
• https://github.com/free5gc/smf/pull/203
• https://github.com/free5gc/free5gc/security/advisories/GHSA-44qj-cghf-9p97

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