Telstra blames missing software update for nationwide outage, undocumented design change
Australian telecom company Telstra revealed that last week's nationwide mobile network outage was caused by a missing software update on a time-synchronisation server and an undocumented design change that maintenance staff were unaware of.
Telstra, in a written submission to a Senate inquiry, has explained the cause of the nationwide mobile network outage that occurred in early July 2026. The company stated that one of its network time protocol (NTP) servers, located in Melbourne, had restarted with an incorrect year – 2006 – due to an underlying software configuration issue. Telstra operates three NTP servers in Melbourne, Sydney, and Perth.
During maintenance, the Melbourne server was shut down and restarted, but due to the software flaw, it came back online with the wrong date. Over the next few hours, the incorrect date propagated slowly across the network, invalidating authentication certificates on other servers. This caused intermittent 'no service' issues for customers, affecting voice calls and mobile data.
Telstra further explained that a prior intentional design change had been made to the equipment to fix an earlier fault, but this change was not properly documented. As a result, maintenance workers arriving at the Melbourne site were unaware of how the device would reset. Additionally, a software update had not been applied to the device; Telstra said that if it had been, the outage might not have occurred.
The company emphasized that the failure was not due to hardware or network architecture, but rather the propagation and acceptance of erroneous date information by interconnected systems that rely on time for security and authentication. Telstra said it had taken full accountability for the outage, calling it unacceptable and vowing to investigate why the design change was undocumented and the software update incomplete.
During the outage, 58,835 calls to the emergency number triple zero connected successfully, while 604 experienced errors. Telstra noted that the triple-zero platform does not use NTP servers, so it was unaffected. Fixed-line calls on the NBN were also unaffected. On Friday, CEO Vicki Brady and other executives are due to appear before a Senate inquiry, established after last year's Optus outage, to explain the incident. The committee chair, Senator Sarah Hanson-Young, said the inquiry aims to uncover the truth and ensure Australians are not left vulnerable.
