CVE-2023-20244Network attack vector

Traffic interruption via inspection-engine block exhaustion

Published Nov 1, 2023 · Updated Aug 2, 2024

Resource exhaustion in the inspection engine of Cisco Firepower Threat Defense allows remote attackers to interrupt device traffic. The engine improperly handles a series of crafted packets and exhausts every available 9,472-byte block. Exploitation requires a Firepower 2100 firewall with an affected inspection feature enabled and causes traffic loss, an unexpected reload, or a state requiring manual reload.

CVSS severity8.6
High
EPSS probability0.77%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Resource exhaustion in the inspection engine of Cisco Firepower Threat Defense allows remote attackers to interrupt device traffic. The engine improperly handles a series of crafted packets and exhausts every available 9,472-byte block. Exploitation requires a Firepower 2100 firewall with an affected inspection feature enabled and causes traffic loss, an unexpected reload, or a state requiring manual reload.

The record

CVE
CVE-2023-20244
Published
Nov 1, 2023
Updated
Aug 2, 2024
Vendor
ClamAV
Product
Cisco Firepower Threat Defense
Classifications
CWE-771, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Nov 1, 2023CVE publishedPublication date reported by the CVE source.
  2. Aug 2, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

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

  1. Affected versionversion=6.2.3
  2. Affected versionversion=6.2.3.1
  3. Affected versionversion=6.2.3.10
  4. Affected versionversion=6.2.3.11
  5. Affected versionversion=6.2.3.12
  6. Affected versionversion=6.2.3.13
  7. Affected versionversion=6.2.3.14
  8. Affected versionversion=6.2.3.15
  9. Affected versionversion=6.2.3.16
  10. Affected versionversion=6.2.3.17
  11. Affected versionversion=6.2.3.18
  12. Affected versionversion=6.2.3.2
  13. Affected versionversion=6.2.3.3
  14. Affected versionversion=6.2.3.4
  15. Affected versionversion=6.2.3.5
  16. Affected versionversion=6.2.3.6
  17. Affected versionversion=6.2.3.7
  18. Affected versionversion=6.2.3.8
  19. Affected versionversion=6.2.3.9
  20. Affected versionversion=6.4.0
  21. Affected versionversion=6.4.0.1
  22. Affected versionversion=6.4.0.10
  23. Affected versionversion=6.4.0.11
  24. Affected versionversion=6.4.0.12
  25. Affected versionversion=6.4.0.13
  26. Affected versionversion=6.4.0.14
  27. Affected versionversion=6.4.0.15
  28. Affected versionversion=6.4.0.16
  29. Affected versionversion=6.4.0.2
  30. Affected versionversion=6.4.0.3
  31. Affected versionversion=6.4.0.4
  32. Affected versionversion=6.4.0.5
  33. Affected versionversion=6.4.0.6
  34. Affected versionversion=6.4.0.7
  35. Affected versionversion=6.4.0.8
  36. Affected versionversion=6.4.0.9
  37. Affected versionversion=6.6.0
  38. Affected versionversion=6.6.0.1
  39. Affected versionversion=6.6.1
  40. Affected versionversion=6.6.3
  41. Affected versionversion=6.6.4
  42. Affected versionversion=6.6.5
  43. Affected versionversion=6.6.5.1
  44. Affected versionversion=6.6.5.2
  45. Affected versionversion=6.6.7
  46. Affected versionversion=6.6.7.1
  47. Affected versionversion=6.7.0
  48. Affected versionversion=6.7.0.1
  49. Affected versionversion=6.7.0.2
  50. Affected versionversion=6.7.0.3
  51. Affected versionversion=7.0.0
  52. Affected versionversion=7.0.0.1
  53. Affected versionversion=7.0.1
  54. Affected versionversion=7.0.1.1
  55. Affected versionversion=7.0.2
  56. Affected versionversion=7.0.2.1
  57. Affected versionversion=7.0.3
  58. Affected versionversion=7.0.4
  59. Affected versionversion=7.0.5
  60. Affected versionversion=7.1.0
  61. Affected versionversion=7.1.0.1
  62. Affected versionversion=7.1.0.3
  63. Affected versionversion=7.2.0
  64. Affected versionversion=7.2.0.1
  65. Affected versionversion=7.2.1
  66. Affected versionversion=7.2.2
  67. Affected versionversion=7.2.3
  68. Affected versionversion=7.3.0
  69. Affected versionversion=7.3.1
  70. Affected versionversion=7.3.1.1

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

ClamAV · Cisco Firepower Threat Defenseversion=6.2.3; version=6.2.3.1; version=6.2.3.10; version=6.2.3.11; version=6.2.3.12; version=6.2.3.13; version=6.2.3.14; version=6.2.3.15; version=6.2.3.16; version=6.2.3.17; version=6.2.3.18; version=6.2.3.2; version=6.2.3.3; version=6.2.3.4; version=6.2.3.5; version=6.2.3.6; version=6.2.3.7; version=6.2.3.8; version=6.2.3.9; version=6.4.0; version=6.4.0.1; version=6.4.0.10; version=6.4.0.11; version=6.4.0.12; version=6.4.0.13; version=6.4.0.14; version=6.4.0.15; version=6.4.0.16; version=6.4.0.2; version=6.4.0.3; version=6.4.0.4; version=6.4.0.5; version=6.4.0.6; version=6.4.0.7; version=6.4.0.8; version=6.4.0.9; version=6.6.0; version=6.6.0.1; version=6.6.1; version=6.6.3; version=6.6.4; version=6.6.5; version=6.6.5.1; version=6.6.5.2; version=6.6.7; version=6.6.7.1; version=6.7.0; version=6.7.0.1; version=6.7.0.2; version=6.7.0.3; version=7.0.0; version=7.0.0.1; version=7.0.1; version=7.0.1.1; version=7.0.2; version=7.0.2.1; version=7.0.3; version=7.0.4; version=7.0.5; version=7.1.0; version=7.1.0.1; version=7.1.0.3; version=7.2.0; version=7.2.0.1; version=7.2.1; version=7.2.2; version=7.2.3; version=7.3.0; version=7.3.1; version=7.3.1.1

Published CVSS scores

8.6Cisco Systems, Inc.CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H

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 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-771Missing Reference to Active Allocated Resource
T1499.004Application or System Exploitation

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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