144 0001943622 XXXXXXXX LIVE 0000926282 ADTRAN HOLDINGS INC 001-41446 901 Explorer Blvd Huntsville AL 35806-2807 256-963-8000 CHRISTOPH GLINGENER Officer Common Morgan Stanley Smith Barney LLC Executive Financial Services

1 New York Plaza 8th Floor New York NY 10004

148392 2331238.32 80998100 05/07/2026 NASDAQ Common 05/07/2026 Exercise of Stock Options Issuer N 148392 05/07/2026 Cash Y The securities to be sold were and will be received upon the exercise of stock options over the next three months. The dates of acquisition and payment were and will be the dates of exercise/sale. 05/07/2026 12/12/2025 /s/ Christoph Glingener