Cisco Zero-Day in Identity Services Engine API Earns Maximum CVSS Score

On September 18, 2026, Cisco disclosed a critical zero-day vulnerability in its Identity Services Engine (ISE), tracked as CVE-2026-76460. The flaw, which received a maximum CVSS score of 10.0, is an authentication bypass issue affecting API endpoints within ISE deployments. According to Dark Reading, the vulnerability allows unauthenticated attackers to bypass authentication controls, potentially gaining unauthorized access to sensitive network access and policy data. The vulnerability is reported as a zero-day, indicating that exploitation may have occurred before the advisory was published. Cisco has released security updates to address the issue, and administrators are strongly advised to apply the latest ISE software patches immediately. The exact attack vectors and any active exploitation in the wild require further validation from Cisco's official security advisory and CISA binding operational directives. Organizations using Cisco ISE should prioritize patching and review their API endpoint exposure to mitigate potential risks.