Open5GS NGAP Handover gmm-sm.c gmm_state_security_mode race condition

A security flaw has been discovered in Open5GS up to 2.7.6. The impacted element is the function gmm_state_security_mode of the file src/amf/gmm-sm.c of the component NGAP Handover. Performing a manipulation results in race condition. The attack can be initiated remotely. The complexity of an attack is rather high. The exploitability is regarded as difficult. The exploit has been released to the public and may be used for attacks. The pull request to fix this issue awaits acceptance.