CVE-2026-44327: free5GC: NEF nnef-oam route group is unauthenticated; no-token requests reach the OAM handler

Vulnerability summary

CVE-2026-44327 is a critical (CVSS 10.0) vulnerability in free5gc. EPSS estimates a 0.53% chance of exploitation in the next 30 days, higher than 43.9% of scored vulnerabilities. 1 public exploit is recorded.

Timeline

1. 27-05-2026
   PublishedVulnerability first disclosed.
2. 28-05-2026
   Last modifiedVulnerability information updated.

Description

free5GC is an open-source implementation of the 5G core network. Prior to 4.2.2, free5GC's NEF mounts the nnef-oam route group without inbound OAuth2/bearer-token authorization. A network attacker who can reach NEF on the SBI can hit the OAM route with no Authorization header at all and the handler returns 200 OK. The current OAM handler is a stub that returns null, but the structural defect is route-group-scoped: the entire OAM route group has no inbound auth middleware, so every future OAM operation added to this group inherits the missing auth boundary by default. This vulnerability is fixed in 4.2.2.

• CWE-306Missing Authentication for Critical FunctionThe product does not perform any authentication for functionality that requires a provable user identity or consumes a significant amount of resources.
• CWE-862Missing AuthorizationThe product does not perform an authorization check when an actor attempts to access a resource or perform an action.