CVE-2021-1224

Multiple Cisco Products Snort TCP Fast Open File Policy Bypass Vulnerability

MEDIUM
5.3
CVSS Score
Published: January 13, 2021 at 09:16 PM UTC
Updated: August 11, 2026 at 07:37 PM UTC
43 products affected across 2 vendorsIOS XeSecure Firewall Threat DefenseSecure Firewall Management Center

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Severity
MEDIUM5.3
Exploit prediction
EPSS 2%
SSVC
No known exploit

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.

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

v < 17.4.1
Affected range stops below 17.4.1, so it looks safe — our inference, not a vendor statement
cisco-1100-4p-integrated-services-router (environment) · cisco-1100-8p-integrated-services-router (environment) · cisco-1101-4p-integrated-services-router (environment) · cisco-1109-2p-integrated-services-router (environment) · cisco-1109-4p-integrated-services-router (environment) · cisco-1111x-8p-integrated-services-router (environment) · cisco-4221-integrated-services-router (environment) · cisco-4321-integrated-services-router (environment) · cisco-4331-integrated-services-router (environment) · cisco-4351-integrated-services-router (environment) · cisco-4431-integrated-services-router (environment) · cisco-4451-x-integrated-services-router (environment) · cisco-4461-integrated-services-router (environment) · cisco-csr-1000v (environment) · cisco-isa-3000 (environment)
All versions
cisco-meraki-mx100 (same device)
All versions
cisco-meraki-mx250 (same device)
All versions
cisco-meraki-mx450 (same device)
All versions
cisco-meraki-mx64 (same device)
All versions
cisco-meraki-mx64w (same device)
All versions
cisco-meraki-mx67 (same device)
All versions
cisco-meraki-mx67c (same device)
All versions
cisco-meraki-mx67w (same device)
All versions
cisco-meraki-mx68 (same device)

Remediation

No guide yet

No remediation guidance has been written for this CVE yet. What the record does show:

SSVC — Action Prioritization

SSVCNo known exploitAutomatablePartial impact

SSVC signals action urgency (what to patch first), separate from CVSS which measures severity.

CVSS

Attack Vector
NETWORK
Complexity
LOW
Privileges
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality
NONE
Integrity
LOW
Availability
NONE
Vector?

Quick Info

StatusMODIFIED
CWE
CWE-693NVD-CWE-Other

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