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

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. According to Cisco, CVE-2026-76504 is being actively exploited in the wild; Cisco PSIRT became aware of the activity in September 2026. Cisco Catalyst SD-WAN Manager systems with ports exposed to the internet are at risk of compromise. The vulnerability affects the product regardless of system configuration, and Cisco has not provided a workaround, however vendor supplied updates are available. Rapid7 strongly recommends that organizations upgrade affected systems to a fixed release on an emergency basis, outside of normal patch cycles, and investigate internet-facing systems for signs of exploitation. Cisco Catalyst SD-WAN Manager was also affected by two critical, unauthenticated peering authentication flaws...