CVE-2021-34753

Cisco Firepower Threat Defense Ethernet Industrial Protocol Policy Bypass Vulnerabilities

MEDIUM

5.3

CVSS Score

Published: November 15, 2024 at 04:14 PM UTC

Updated: August 11, 2026 at 07:40 PM UTC

2 products affected across 1 vendorSecure Firewall Threat DefenseFirepower Threat Defense

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Severity

MEDIUM5.3

Exploit prediction

EPSS 0.7%

SSVC

No known exploit

Description

A vulnerability in the payload inspection for Ethernet Industrial Protocol (ENIP) traffic for Cisco Firepower Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to bypass configured rules for ENIP traffic. This vulnerability is due to incomplete processing during deep packet inspection for ENIP packets. An attacker could exploit this vulnerability by sending a crafted ENIP packet to the targeted interface. A successful exploit could allow the attacker to bypass configured access control and intrusion policies that should trigger and drop for the ENIP packet.

Affected

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

Secure Firewall Threat Defense · Cisco

95%

v < 6.4.0.136.5.0 ≤ v < 6.6.5.16.7.0 ≤ v < 6.7.0.37.0.0

Affected range stops below 6.4.0.13, so it looks safe — our inference, not a vendor statement

Affected range stops below 6.6.5.1, so it looks safe — our inference, not a vendor statement

Affected range stops below 6.7.0.3, so it looks safe — our inference, not a vendor statement

Firepower Threat Defense · Cisco

60%

v < 6.4.0.136.5.0 ≤ v < 6.6.5.16.7.0 ≤ v < 6.7.0.37.0.0 ≤ v < 7.0.16.5.0 6.7.0 7.0.0

Affected range stops below 6.4.0.13, so it looks safe — our inference, not a vendor statement

Affected range stops below 6.6.5.1, so it looks safe — our inference, not a vendor statement

Affected range stops below 6.7.0.3, so it looks safe — our inference, not a vendor statement

Affected range stops below 7.0.1, so it looks safe — our inference, not a vendor statement

Remediation

No guide yet

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

Patch and advisory references

https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-ftd-enip-bypass-eFsxd8KP

References (1)

Vendor Advisory

Source: [email protected]

https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-ftd-enip-bypass-eFsxd8KP

SSVC — Action Prioritization

SSVCNo known exploitAutomatablePartial impact

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

CVSS

5.3MEDIUM[email protected]

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

Vector?

Quick Info

StatusANALYZED

CWE

CWE-284

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