The vulnerability in free5GC UDR (<= 1.4.2) is due to improper checking for unusual or exceptional conditions (CWE-754) in the POST handler at /nudr-dr/v2/policy-data/subs-to-notify. Specifically, the service fails to halt processing when errors occur during request body retrieval or deserialization, resulting in a fail-open condition. This behavior may cause the creation of policy data notification subscriptions with invalid, empty, or partially processed data depending on downstream processing. The CVSS 4.0 base score is 6.9, reflecting network attack vector, low attack complexity, no privileges or user interaction required, and limited impact on integrity and system availability. No patch or vendor advisory with remediation is currently available.

The vulnerability allows an attacker to cause the UDR service to create policy data notification subscriptions with malformed or incomplete data. This could potentially lead to inconsistent or unintended policy data states within the 5G core network environment. The impact is limited to integrity and system availability aspects with no direct confidentiality impact. There are no known exploits in the wild at this time.

As of the publication date, no official fix or patch is available for this vulnerability. Users should monitor the free5GC project for updates or patches addressing this issue. Until a patch is released, consider implementing additional input validation or request filtering at network boundaries to reduce exposure. Avoid deploying vulnerable versions in production environments where possible.