Free5GC up to 1.4.1 UDM Nudm_UEAU input validation

Summaryinfo

A vulnerability, which was classified as problematic, was found in Free5GC up to 1.4.1. This impacts the function Nudm_UEAU of the component UDM. Such manipulation leads to input validation. This vulnerability is referenced as CVE-2026-27642. It is possible to launch the attack remotely. No exploit is available. It is best practice to apply a patch to resolve this issue.

Detailsinfo

A vulnerability, which was classified as problematic, has been found in Free5GC up to 1.4.1. Affected by this issue is the function Nudm_UEAU of the component UDM. The manipulation with an unknown input leads to a input validation vulnerability. Using CWE to declare the problem leads to CWE-20. The product receives input or data, but it does not validate or incorrectly validates that the input has the properties that are required to process the data safely and correctly. Impacted is confidentiality. CVE summarizes:

free5gc UDM provides Unified Data Management (UDM) for free5GC, an open-source project for 5th generation (5G) mobile core networks. In versions up to and including 1.4.1, remote attackers can inject control characters (e.g., %00) into the supi parameter, triggering internal URL parsing errors (net/url: invalid control character). This exposes system-level error details and can be used for service fingerprinting. All deployments of free5GC using the UDM Nudm_UEAU service may be affected. free5gc/udm pull request 75 contains a fix for the issue. No direct workaround is available at the application level. Applying the official patch is recommended.

The advisory is available at github.com. This vulnerability is handled as CVE-2026-27642 since 02/20/2026. The exploitation is known to be easy. The attack may be launched remotely. No form of authentication is required for exploitation. Technical details are known, but there is no available exploit.

Applying the patch a7af2321ddea6368c43835f90f6d1b9d67dd2ea1 is able to eliminate this problem. The bugfix is ready for download at github.com.

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Productinfo

Name

• Free5GC

Version

• 1.4.0
• 1.4.1

License

• open-source

Website

• Product: https://github.com/free5gc/free5gc/

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