Critical Cisco Catalyst SD-WAN Manager API authentication bypass exploited in the wild (CVE-2026-76504)

Overview On September 30, 2026, Cisco published a security advisory for CVE-2026-76504 , a critical API authentication bypass vulnerability affecting Cisco Catalyst SD-WAN Manager. The vulnerability has a CVSSv3.1 score of 9.8 and results from improper handling of URL encoding ( CWE-177 ). An unauthenticated, remote attacker can send a crafted HTTP request that bypasses an authentication rule for a specific API endpoint, gaining access to the API with the privileges of the admin user.