F´ (F Prime) is a framework that enables development and deployment of spaceflight and other embedded software applications. Prior to 4.2.0, Fw::FilePacket deserialization used by Svc::FileUplink is vulnerable because Header deserialization casts the byte to the Type enum without validating its range and FilePacket::fromSerialBuffer reaches a default FW_ASSERT. When a network file packet contains an unknown file-packet type byte, the assertion aborts or resets the default Ref application process, causing denial of service. This issue is fixed in version 4.2.0.