Multiple Cisco products are affected by a vulnerability with TCP Fast Open (TFO) when used in conjunction with the Snort detection engine that could allow an unauthenticated, remote attacker to bypass a configured file policy for HTTP. The vulnerability is due to incorrect detection of the HTTP payload if it is contained at least partially within the TFO connection handshake. An attacker could exploit this vulnerability by sending crafted TFO packets with an HTTP payload through an affected device. A successful exploit could allow the attacker to bypass configured file policy for HTTP packets and deliver a malicious payload.
Use CWE-693, Cisco vendor hub and Firepower Threat Defense product page to widen CVE-2021-1224 into its surrounding weakness, vendor, and product context.
Compare it with CVE-2025-20333, CVE-2025-20362 and CVE-2024-20412 for nearby disclosures in the same product family. Additional editorial context is available in Weekly Security Roundup: Navigating the April 2026 Threat Landscape and Critical Framework Exploits.