NTT Docomo hit by 5G SA outage and suspected server breach on same day

NTT Docomo's standalone 5G network has been unstable since 11:18 a.m. Thursday, knocking out voice calls, data and text messaging for customers across Japan. The carrier said it had found no signs of a cyberattack behind the disruption, and that it is still investigating the cause.

The damage is contained but real. Only the 5G SA service — the standalone variant of 5G that runs on a dedicated core rather than anchoring to 4G infrastructure — is affected. Other 5G services, 4G services and emergency calls all continue to work. MVNOs and other businesses that ride on NTT Docomo's network are unaffected too, the company confirmed.

What should affected customers do?

There is a workaround, and it's a simple one. NTT Docomo advises customers to switch to 4G in their network settings, then restart their phones or toggle airplane mode on and off. That may restore service while engineers work on the 5G SA core. It's an inelegant fix, but it's the difference between a broken phone and a slightly slower one.

A second, separate incident

The outage wasn't the only bad news on Docomo's Thursday. In an earlier announcement the same day, the operator said it had suspended its online shop and the "My docomo" customer portal after determining that an outside party had likely gained unauthorized access to its servers.

That suspension began around 1:05 a.m. — roughly ten hours before the 5G SA trouble started. Customers have since been unable to sign up for mobile plans, check bills or make contract changes through the affected services.

NTT Docomo is investigating whether any data was leaked in the suspected intrusion. It has not said when the portal and online shop will return.

Two incidents, one uneasy question

The carrier has drawn no line between the two events, and it says the network disruption shows no signs of a cyberattack. Still, a nationwide service fault and a suspected server breach landing on the same calendar day is the kind of coincidence that keeps an operator's press office busy.

The 5G SA problem is the more visible failure. Standalone 5G is the architecture operators tout as the future of the technology — the version that unlocks network slicing and low-latency use cases. When its core wobbles, customers notice in the most basic way: calls that don't connect and texts that don't send.

By contrast, the portal suspension is quieter but potentially more costly. Unauthorized server access raises questions about personal and billing data, and Docomo's own statement that a leak is still being investigated leaves that question open.

What happens next?

For now, the carrier's priorities are plain: restore 5G SA stability, confirm whether the server intrusion leaked data, and bring the online shop and My docomo portal back online. It has given no timeline for any of the three. Customers who need a working phone today can take the 4G escape hatch; those waiting on answers about their data will have to wait a little longer.