U.S. officials seeking to convince allies not to use Huawei in their 5G networks are alerting a security flaw that allows the Chinese government-backed telecommunications giant to purloin sensitive information secretly.

The United States has pursued an aggressive campaign to block allies from using Huawei in their 5G network plans, arguing that the company’s close ties to the Chinese government pose a national security risk. The U.S. has lobbied its intelligence-sharing partners most aggressively, including Five Eyes members the United Kingdom, Australia, Canada, and New Zealand.