CVE-2026-40246: Free5gc Improper Authorization (CVSS 8.7)

free5GC is an open-source implementation of the 5G core network. Prior to 4.2.2, the free5GC UDM component fails to validate the supi path parameter in six GET handlers of the nudm-sdm (Subscriber Data Management) service. An unauthenticated attacker can inject control characters into the SUPI parameter, causing UDM to forward a malformed request to UDR and return a 500 Internal Server Error response that exposes internal infrastructure details. This vulnerability is fixed in 4.2.2.

free5GC is an open-source implementation of the 5G core network. In versions 4.2.1 and below of the UDR service, the handler for creating or updating Traffic Influence Subscriptions checks whether the influenceId path segment equals subs-to-notify, but does not return after sending the HTTP 404 response when validation fails. Execution continues and the subscription is created or overwritten regardless. An unauthenticated attacker with access to the 5G Service Based Interface can create or overwrite arbitrary Traffic Influence Subscriptions, including injecting attacker-controlled notificationUri values and arbitrary SUPIs, by supplying any value for the influenceId path segment. A patched version was not available at the time of publication.

free5GC is an open-source implementation of the 5G core network. In versions 4.2.1 and below of the UDR service, the handler for reading Traffic Influence Subscriptions checks whether the influenceId path segment equals subs-to-notify, but does not return after sending the HTTP 404 response when validation fails. Execution continues and the subscription data is returned alongside the 404 response. An unauthenticated attacker with access to the 5G Service Based Interface can read arbitrary Traffic Influence Subscriptions, including SUPIs/IMSIs, DNNs, S-NSSAIs, and callback URIs, by supplying any value for the influenceId path segment. A patched version was not available at the time of publication.

An issue in Free5GC v.4.2.0 and before allows a remote attacker to cause a denial of service via the function HandleAuthenticationFailure of the component AMF

Free5GC is an open-source Linux Foundation project for 5th generation (5G) mobile core networks. Versions prior to 1.4.2 are vulnerable to null byte injection in URL path parameters. A remote attacker can inject null bytes (URL-encoded as %00) into the supi path parameter of the UDM's Nudm_SubscriberDataManagement API. This causes URL parsing failure in Go's net/url package with the error "invalid control character in URL", resulting in a 500 Internal Server Error. This null byte injection vulnerability can be exploited for denial of service attacks. When the supi parameter contains null characters, the UDM attempts to construct a URL for UDR that includes these control characters. Go's URL parser rejects them, causing the request to fail with 500 instead of properly validating input and returning 400 Bad Request. This issue has been fixed in version 1.4.2.

Free5GC is an open-source Linux Foundation project for 5th generation (5G) mobile core networks. Versions prior to 1.4.2 are vulnerable to procedure panic caused by Nil Pointer Dereference in the /sdm-subscriptions endpoint. A remote attacker can cause the UDM service to panic and crash by sending a crafted POST request to the /sdm-subscriptions endpoint with a malformed URL path containing path traversal sequences (../) and a large JSON payload. The DataChangeNotificationProcedure function in notifier.go attempts to access a nil pointer without proper validation, causing a complete service crash with "runtime error: invalid memory address or nil pointer dereference". Exploitation would result in UDM functionality disruption until recovery by restart. This issue has been fixed in version 1.4.2.