{"id":"CVE-2021-1224","title":"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","summary":"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. T…","severity":"medium","cvss":5.8,"cvssVector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:L/A:N","cwe":["CWE-693"],"vendor":"cisco","product":"secure_firewall_management_center","affected":["secure_firewall_management_center = 2.9.14.0","secure_firewall_management_center = 2.9.15","secure_firewall_management_center = 2.9.16","secure_firewall_management_center = 2.9.17","secure_firewall_management_center = 2.9.18","secure_firewall_management_center = 3.0.1","secure_firewall_threat_defense < 6.7.0","ios_xe < 17.4.1","snort < 2.9.17","meraki_mx64_firmware","meraki_mx64w_firmware","meraki_mx67_firmware","meraki_mx67c_firmware","meraki_mx67w_firmware","meraki_mx68_firmware","meraki_mx68cw_firmware","meraki_mx68w_firmware","meraki_mx100_firmware","meraki_mx84_firmware","meraki_mx250_firmware","meraki_mx450_firmware"],"patched":["secure_firewall_threat_defense 6.7.0","ios_xe 17.4.1","snort 2.9.17"],"published":"2021-01-13","updated":"2026-08-11","source":"NVD","sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2021-1224","references":[{"url":"https://lists.debian.org/debian-lts-announce/2023/02/msg00011.html","label":"psirt@cisco.com"},{"url":"https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-snort-tfo-bypass-MmzZrtes","label":"psirt@cisco.com"},{"url":"https://www.debian.org/security/2023/dsa-5354","label":"psirt@cisco.com"},{"url":"https://lists.debian.org/debian-lts-announce/2023/02/msg00011.html","label":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-snort-tfo-bypass-MmzZrtes","label":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"https://www.debian.org/security/2023/dsa-5354","label":"af854a3a-2127-422b-91ae-364da2661108"}],"tags":["nvd"],"epss":0.02005,"epssPercentile":0.79943,"ingestedAt":"2026-08-18T12:28:06.808Z","slug":"CVE-2021-1224","body":"## Overview\n\nMultiple 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.\n\n## Affected\n\n- `secure_firewall_management_center = 2.9.14.0`\n- `secure_firewall_management_center = 2.9.15`\n- `secure_firewall_management_center = 2.9.16`\n- `secure_firewall_management_center = 2.9.17`\n- `secure_firewall_management_center = 2.9.18`\n- `secure_firewall_management_center = 3.0.1`\n- `secure_firewall_threat_defense < 6.7.0`\n- `ios_xe < 17.4.1`\n- `snort < 2.9.17`\n- `meraki_mx64_firmware`\n- `meraki_mx64w_firmware`\n- `meraki_mx67_firmware`\n- `meraki_mx67c_firmware`\n- `meraki_mx67w_firmware`\n- `meraki_mx68_firmware`\n- `meraki_mx68cw_firmware`\n- `meraki_mx68w_firmware`\n- `meraki_mx100_firmware`\n- `meraki_mx84_firmware`\n- `meraki_mx250_firmware`\n- `meraki_mx450_firmware`\n\n## Remediation\n\nUpgrade past the affected range:\n\n- `secure_firewall_threat_defense 6.7.0`\n- `ios_xe 17.4.1`\n- `snort 2.9.17`","depth":"sunlit","depthScore":32,"depthScoreParts":{"impact":31.9,"likelihood":0.4,"exploitation":0,"ransomware":0},"changes":[]}