A newly found flaw in widely used networking software leaves tens of thousands of computers potentially vulnerable to an attack similar to that caused by WannaCry, which infected more than 300,000 computers worldwide, cybersecurity researchers said Thursday.

The U.S. Department of Homeland Security on Wednesday announced the vulnerability, which could be exploited to take control of an affected computer, and urged users and administrators to apply a patch.

Rebekah Brown of Rapid7, a cybersecurity company, told Reuters that there were no signs yet of attackers exploiting the vulnerability in the 12 hours since its discovery was announced.