A critical security vulnerability in Cisco’s SD-WAN vManage software could allow a remote, unauthenticated attacker to gain read and limited write permissions, and access data.

The bug carries a score of 9.1 out of 10 on the CVSS vulnerability-severity scale, and it exists in the vManage API, which is used to monitor and configure Cisco devices running on an overlay network, the company explained.

“This vulnerability is due to insufficient request validation when using the REST API feature,” according to Cisco’s July 12 advisory. “An attacker could exploit this vulnerability by sending a crafted API request to an affected vManage instance.”