CVE-2021-34754Network attack vector

ENIP policy bypass via incomplete packet inspection

Published Oct 27, 2021 · Updated Nov 7, 2024

Access-control bypass in Cisco Firepower Threat Defense Software allows remote attackers to evade ENIP policy enforcement via crafted packets. The ENIP deep-packet inspection path incompletely processes crafted ENIP packets, so matching access-control and intrusion rules are not activated. Exposure requires an interface accepting attacker-supplied ENIP traffic and a configuration that detects and blocks ENIP; impact is limited to policy bypass for those packets.

CVSS severity5.8
Medium
EPSS probability1.00%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Access-control bypass in Cisco Firepower Threat Defense Software allows remote attackers to evade ENIP policy enforcement via crafted packets. The ENIP deep-packet inspection path incompletely processes crafted ENIP packets, so matching access-control and intrusion rules are not activated. Exposure requires an interface accepting attacker-supplied ENIP traffic and a configuration that detects and blocks ENIP; impact is limited to policy bypass for those packets.

The record

CVE
CVE-2021-34754
Published
Oct 27, 2021
Updated
Nov 7, 2024
Vendor
ClamAV
Product
Cisco Firepower Threat Defense Software
Classifications
CWE-284
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Oct 27, 2021CVE publishedPublication date reported by the CVE source.
  2. Nov 7, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=n/a

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

ClamAV · Cisco Firepower Threat Defense Softwareversion=n/a

Published CVSS scores

7.5NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
5.8CiscoCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:L/A:N/E:X/RL:X/RC:X

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-284Improper Access Control

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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