Free5GC up to 4.2.1 gNB security check

Summaryinfo

A vulnerability described as problematic has been identified in Free5GC up to 4.2.1. The impacted element is an unknown function of the component gNB Handler. Executing a manipulation can lead to security check. This vulnerability is handled as CVE-2026-42081. The attack can only be done within the local network. There is not any exploit available. Upgrading the affected component is recommended.

Detailsinfo

A vulnerability was found in Free5GC up to 4.2.1. It has been declared as problematic. This vulnerability affects an unknown code block of the component gNB Handler. The manipulation with an unknown input leads to a security check vulnerability. The CWE definition for the vulnerability is CWE-358. The product does not implement or incorrectly implements one or more security-relevant checks as specified by the design of a standardized algorithm, protocol, or technique. As an impact it is known to affect integrity, and availability. CVE summarizes:

free5GC is an open-source implementation of the 5G core network. Prior to 4.2.2, the AMF in Free5GC does not verify the UE Security Capabilities received in NGAP PathSwitchRequest messages against its locally stored values, as mandated by 3GPP TS 33.501 §6.7.3.1. A malicious gNB can overwrite the AMF's stored UE security capabilities with arbitrary values, which are then propagated in PathSwitchRequest Acknowledge messages and subsequent Handover Request messages. This leads to persistent handover denial-of-service for affected UEs. This vulnerability is fixed in 4.2.2.

The advisory is available at github.com. This vulnerability was named CVE-2026-42081 since 04/23/2026. The exploitation appears to be easy. Access to the local network is required for this attack. No form of authentication is required for a successful exploitation. The technical details are unknown and an exploit is not available. This vulnerability is assigned to T1211 by the MITRE ATT&CK project.

Upgrading to version 4.2.2 eliminates this vulnerability.

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Productinfo

Name

• Free5GC

Version

• 4.2.0
• 4.2.1

Website

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

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