CVE-2021-1223Network attack vector

File policy bypass via malformed HTTP ranges

Published Jan 13, 2021 · Updated Nov 12, 2024

Improper HTTP Range handling in Cisco Firepower Threat Defense before 6.7.0 allows remote attackers to bypass an HTTP file policy. The Snort detection engine incorrectly handles crafted HTTP Range headers, allowing matching content to evade the configured policy. Exploitation requires traffic to traverse an affected device with that policy configured and permits malicious-payload delivery past the control.

CVSS severity5.8
Medium
EPSS probability1.98%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper HTTP Range handling in Cisco Firepower Threat Defense before 6.7.0 allows remote attackers to bypass an HTTP file policy. The Snort detection engine incorrectly handles crafted HTTP Range headers, allowing matching content to evade the configured policy. Exploitation requires traffic to traverse an affected device with that policy configured and permits malicious-payload delivery past the control.

The record

CVE
CVE-2021-1223
Published
Jan 13, 2021
Updated
Nov 12, 2024
Vendor
ClamAV
Product
Cisco Firepower Threat Defense Software
Classifications
CWE-693, T1562.001
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jan 13, 2021CVE publishedPublication date reported by the CVE source.
  2. Nov 12, 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?

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  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
5.8Cisco Systems, Inc.CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:L/A:N
5.0NIST NVDAV:N/AC:L/Au:N/C:N/I:P/A:N

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.

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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-693Protection Mechanism Failure
T1562.001Impair Defenses: Disable or Modify Tools

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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