CVE-2021-1494Network attack vector

File-policy bypass via malformed HTTP headers

Published Nov 15, 2024 · Updated Nov 15, 2024

Protection mechanism failure in Cisco UTD Snort IPS Engine Software and Firepower Threat Defense allows remote attackers to bypass HTTP file policies. The Snort HTTP detection engine incorrectly handles specific HTTP header parameters, allowing crafted packets to evade a configured file policy and carry a malicious payload through the device. Exploitation requires traffic to traverse an affected device with the Snort HTTP Detection Engine File Policy configured; no confidentiality or availability impact is reported.

CVSS severity5.8
Medium
EPSS probability1.10%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Protection mechanism failure in Cisco UTD Snort IPS Engine Software and Firepower Threat Defense allows remote attackers to bypass HTTP file policies. The Snort HTTP detection engine incorrectly handles specific HTTP header parameters, allowing crafted packets to evade a configured file policy and carry a malicious payload through the device. Exploitation requires traffic to traverse an affected device with the Snort HTTP Detection Engine File Policy configured; no confidentiality or availability impact is reported.

The record

CVE
CVE-2021-1494
Published
Nov 15, 2024
Updated
Nov 15, 2024
Vendor
ClamAV
Product
Cisco UTD Snort IPS Engine Software
Classifications
CWE-693, T1562.001
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Nov 15, 2024CVE publishedPublication date reported by the CVE source.
  2. Nov 15, 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=0 <16.12.5
  2. Affected versionversion=16.12.1a
  3. Affected versionversion=16.12.2
  4. Affected versionversion=16.12.3
  5. Affected versionversion=16.12.4
  6. Affected versionversion=16.6.1
  7. Affected versionversion=16.6.5
  8. Affected versionversion=16.6.6
  9. Affected versionversion=16.6.7a
  10. Affected versionversion=16.6.9
  11. Affected versionversion=17.1.1
  12. Affected versionversion=17.1 <17.3.3
  13. Affected versionversion=17.2.1r
  14. Affected versionversion=17.3.1a
  15. Affected versionversion=17.3.2
  16. Affected versionversion=17.4 <17.4.1
  17. Affected versionversion=3.17.0S
  18. Affected versionversion=3.17.1S
  19. Affected versionversion=Denali-16.3.3
  20. Affected versionversion=Denali-16.3.4
  21. Affected versionversion=Denali-16.3.5
  22. Affected versionversion=Denali-16.3.7
  23. Affected versionversion=Denali-16.3.9
  24. Affected versionversion=Everest-16.6.2
  25. Affected versionversion=Everest-16.6.3
  26. Affected versionversion=Everest-16.6.4
  27. Affected versionversion=Fuji-16.9.2
  28. Affected versionversion=Fuji-16.9.3
  29. Affected versionversion=Fuji-16.9.4
  30. Affected versionversion=Fuji-16.9.5
  31. Affected versionversion=Fuji-16.9.6
  32. Affected versionversion=Fuji-16.9.7

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

ClamAV · Cisco UTD Snort IPS Engine Softwareversion=0 <16.12.5; version=16.12.1a; version=16.12.2; version=16.12.3; version=16.12.4; version=16.6.1; version=16.6.5; version=16.6.6; version=16.6.7a; version=16.6.9; version=17.1.1; version=17.1 <17.3.3; version=17.2.1r; version=17.3.1a; version=17.3.2; version=17.4 <17.4.1; version=3.17.0S; version=3.17.1S; version=Denali-16.3.3; version=Denali-16.3.4; version=Denali-16.3.5; version=Denali-16.3.7; version=Denali-16.3.9; version=Everest-16.6.2; version=Everest-16.6.3; version=Everest-16.6.4; version=Fuji-16.9.2; version=Fuji-16.9.3; version=Fuji-16.9.4; version=Fuji-16.9.5; version=Fuji-16.9.6; version=Fuji-16.9.7
ClamAV · Cisco Firepower Threat Defenseversion=0 <6.4.0.12; version=6.5.0 <6.6.4; version=6.7.0 <6.7.0.2; version=N/A

Published CVSS scores

5.8Cisco Systems, Inc.CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:L/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.

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

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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