An expired certificate was the cause of a data outage across O2 and SoftBank mobile services in the United Kingdom and Japan, respectively, Ericsson has revealed.
"An initial root cause analysis indicates that the main issue was an expired certificate in the software versions installed with these customers," Ericsson said.
"A complete and comprehensive root cause analysis is still in progress. Our focus is now on solving the immediate issues."
The issue affected nodes in the core networks of customers using two software versions of the Serving GPRS Support Node - Mobility Management Entity (SGSN-MME), Ericsson said, adding that it had taken immediate action to enable service restoration.
"The faulty software that has caused these issues is being decommissioned, and we apologise not only to our customers but also to their customers," Ericsson CEO Börje Ekholm said.
"We work hard to ensure that our customers can limit the impact and restore their services as soon as possible."
Most network services have now been restored, Ericsson said, with O2 confirming in a statement that its 3G data service is returning and was expected to be restored fully by 9.30pm GMT on Thursday.
O2 will work on restoring the remainder of its services throughout the night.
"Our technical teams will continue working hard with Ericsson engineers to restore 4G, which will bring us back to full network service," O2 said on Thursday night.
"Our teams, together with Ericsson, are doing everything we can," Telefonica O2 UK CEO Mark Evans added.
"We will continue to work with Ericsson through the night, who have assured us that a full service will be restored for customers by the morning. We fully appreciate it's been a poor experience and we are really sorry."
Earlier on Thursday, O2 had said the data network outage was the result of a "global software issue".
Over in Japan, SoftBank said its outage extended from 1.39pm until 6.04pm JST on Thursday, with SoftBank and Y!mobile 4G LTE mobile phone services, Ouchi-No-Denwa fixed-line services, and SoftBank Air services affected.
The outage was "caused by Ericsson-made software errors related to its packet switches, covering our customers nationwide", SoftBank explained. It is still investigating how many customers were impacted.
"At 1.39pm on Thursday, December 6, 2018, the SoftBank Network Center detected software's malfunction in all of the packet switching machines manufactured by Ericsson, which are installed at the Tokyo Center and the Osaka Center, covering our mobile customers nationwide," SoftBank said.
"After the incident, SoftBank received a report from Ericsson that the software has been in operation since nine months ago and the failure caused by the same software also occurred simultaneously in other telecom carriers across 11 countries, which installed the same Ericsson-made devices.
"The network was recovered to the normal operation by adapting the older version of the software to all packet switching machines."
Updated: O2 blames problem on supplier's software, says the problem could be hitting other networks around the world too.
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