This book constitutes the refereed proceedings of six International Workshops that were held in conjunction with the 26th European Symposium on Research in Computer Security, ESORICS 2021, which took place during October 4-6, 2021. The conference was initially planned to take place in Darmstadt, Germany, but changed to an online event due to the COVID-19 pandemic.

The 32 papers included in these proceedings stem from the following workshops:

• the 7th Workshop on the Security of Industrial Control Systems and of Cyber-Physical Systems, CyberICPS 2021, which accepted 7 papers from 16 submissions;
• the 5th International Workshop on Security and Privacy Requirements Engineering, SECPRE 2021, which accepted 5 papers from 8 submissions;
• the 4th International Workshop on Attacks and Defenses for Internet-of-Things, ADIoT 2021, which accepted 6 full and 1 short paper out of 15 submissions;
•  the 3rd Workshop on Security, Privacy, Organizations, andSystems Engineering, SPOSE 2021, which accepted 5 full and 1 short paper out of 13 submissions.
• the 2nd Cyber-Physical Security for Critical Infrastructures Protection, CPS4CIP 2021, which accepted 3 full and 1 short paper out of 6 submissions; and
•  the 1st International Workshop on Cyber Defence Technologies and Secure Communications at the Network Edge, CDT & SECOMANE 2021, which accepted 3 papers out of 7 submissions.