F´ (F Prime) is a framework that enables development and deployment of spaceflight and other embedded software applications. Prior to version 4.2.0, the bounds check byteOffset + dataSize > fileSize uses U32 addition that wraps around on overflow. An attacker-crafted DataPacket with byteOffset=0xFFFFFF9C and dataSize=100 overflows to 0, bypassing the check entirely. The subsequent file write proceeds at the original ~4GB offset. Additionally, Svc/FileUplink/File.cpp:20-31 performs no sanitization on the destination file path. Combined, these allow writing arbitrary data to any file at any offset. The impact is arbitrary file write leading to remote code execution on embedded targets. Note that this is a logic bug. ASAN does not detect it because all memory accesses are within valid buffers — the corruption occurs in file I/O. Version 4.2.0 contains a patch. No known workarounds are available.