A denial-of-service vulnerability exists in the omec-project UPF (pfcpiface component) in version upf-epc-pfcpiface:2.1.3-dev. After PFCP association is established, a PFCP Session Establishment Request that is missing the mandatory F-SEID (CPF-SEID) Information Element is not properly validated. The session establishment handler calls IE.FSEID() on a nil pointer, which triggers a panic and terminates the UPF process. An attacker who can send PFCP Session Establishment Request messages to the UPF's N4/PFCP endpoint can exploit this issue to repeatedly crash the UPF and disrupt user-plane services.