A security flaw has been discovered in NASA cFS up to 7.0.1. The affected element is the function CFE_SB_GetUserDataLength of the file src/cFS/cfe/modules/sb/fsw/src/cfe_sb_util.c of the component cFE Software Bus. Performing a manipulation of the argument TotalMsgSize/HdrSize results in integer underflow. It is possible to initiate the attack remotely. The vendor was contacted early about this disclosure but did not respond in any way.