Dear users,

We would like to inform that on Tuesday, June 23, 2026, from 16:30 to 21:40, the CS OTE system, including automatic communication, will be unavailable due to the deployment of system updates and new functionalities. Gas nominations entered into the NET4GAS system during the OTE outage must be re-nominated.

Planned outage schedule:

• Unavailability of automatic communication for markets: 16:35–17:35

• Minor disruptions of the Portal (partially also mobile applications): 16:45–19:30

• Login and signature verification unavailable: 18:55–19:30

• Public website unavailable: 17:30–17:50

• OTE-COM shutdown: 18:30–21:10

We further inform participants that, as part of enhancing service security, the following measures will be introduced in the OTE central system environment for validation of used algorithms and minimum RSA key lengths. These measures apply to the OTE Portal and the OTECOM application, including automatic OTECOM communication:

• Prohibition of hash algorithms MD5 and SHA1

• Prohibition of the use of RSA keys shorter than 2048 bits

Thank you for your understanding, and we apologize for any inconvenience caused.