This book constitutes the refereed proceedings of the 40th IFIP WG 11.3 Annual Conference on Data and Applications Security and Privacy, DBSec 2026, held in Arlington, VA, USA, during July 28-30, 2026.

The 18 full papers and 10 short papers included in this book were carefully reviewed and selected from 64 submissions. The papers present research from academia, industry, and government on both theoretical and practical aspects of information security.