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Vulnerability record · CVE-2021-1224 · published 13 January 2021

CVE-2021-1224: Cisco secure firewall management center vulnerability

Cisco · Secure Firewall Management Center

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.

5.3 CVSS 3.1 Medium EPSS 2.0% · top 19.2% CWE-693 · CWE-693
5.3CVSS 3.1 base score, v2 5.0
2.0%EPSS exploitation probability, 30 days
NoNot in CISA KEV
16Affected product versions listed by NVD
6References
11 Aug 2026Last modified by NVD

Description

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.

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N

Affected products

16 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
https://lists.debian.org/debian-lts-announce/2023/02/msg00011.html
https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-snort-tfo-bypass-MmzZrtes Vendor Advisory
https://www.debian.org/security/2023/dsa-5354
https://lists.debian.org/debian-lts-announce/2023/02/msg00011.html
https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-snort-tfo-bypass-MmzZrtes Vendor Advisory
https://www.debian.org/security/2023/dsa-5354

Track CVE-2021-1224 inside VULONE

Watch it alongside the ransomware crews, C2 infrastructure and forum chatter that reference it, query it through the API and pull it into your SIEM over TAXII.

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Related vulnerabilities

Same products first, then exploited flaws of the same weakness class.

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Source: NIST National Vulnerability Database (record CVE-2021-1224), CISA KEV, FIRST EPSS (scores of 2026-10-14). This page is refreshed as NVD updates the record.