CVE-2023-20256Network attack vector

ACL bypass via faulty per-user-override rules

Published Nov 1, 2023 · Updated Nov 21, 2024

Authentication bypass in Cisco ASA and FTD Software allows remote attackers to route prohibited traffic through an affected device. A logic error constructs and applies per-user-override rules incorrectly, allowing traffic to bypass the configured interface ACL. Exposure requires specific VPN, vpn-filter, per-user-override, and live-tunnel conditions; successful exploitation grants access to protected resources.

CVSS severity5.0
Medium
EPSS probability0.56%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Authentication bypass in Cisco ASA and FTD Software allows remote attackers to route prohibited traffic through an affected device. A logic error constructs and applies per-user-override rules incorrectly, allowing traffic to bypass the configured interface ACL. Exposure requires specific VPN, vpn-filter, per-user-override, and live-tunnel conditions; successful exploitation grants access to protected resources.

The record

CVE
CVE-2023-20256
Published
Nov 1, 2023
Updated
Nov 21, 2024
Vendor
ClamAV
Product
Cisco Adaptive Security Appliance (ASA) Software
Classifications
CWE-290, T1190
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Nov 1, 2023CVE publishedPublication date reported by the CVE source.
  2. Nov 21, 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=9.12.4.10
  2. Affected versionversion=9.12.4.13
  3. Affected versionversion=9.12.4.18
  4. Affected versionversion=9.12.4.2
  5. Affected versionversion=9.12.4.24
  6. Affected versionversion=9.12.4.26
  7. Affected versionversion=9.12.4.29
  8. Affected versionversion=9.12.4.30
  9. Affected versionversion=9.12.4.35
  10. Affected versionversion=9.12.4.37
  11. Affected versionversion=9.12.4.38
  12. Affected versionversion=9.12.4.39
  13. Affected versionversion=9.12.4.4
  14. Affected versionversion=9.12.4.40
  15. Affected versionversion=9.12.4.41
  16. Affected versionversion=9.12.4.47
  17. Affected versionversion=9.12.4.48
  18. Affected versionversion=9.12.4.50
  19. Affected versionversion=9.12.4.52
  20. Affected versionversion=9.12.4.54
  21. Affected versionversion=9.12.4.55
  22. Affected versionversion=9.12.4.56
  23. Affected versionversion=9.12.4.7
  24. Affected versionversion=9.12.4.8
  25. Affected versionversion=9.14.1.10
  26. Affected versionversion=9.14.1.15
  27. Affected versionversion=9.14.1.19
  28. Affected versionversion=9.14.1.30
  29. Affected versionversion=9.14.2
  30. Affected versionversion=9.14.2.13
  31. Affected versionversion=9.14.2.15
  32. Affected versionversion=9.14.2.4
  33. Affected versionversion=9.14.2.8
  34. Affected versionversion=9.14.3
  35. Affected versionversion=9.14.3.1
  36. Affected versionversion=9.14.3.11
  37. Affected versionversion=9.14.3.13
  38. Affected versionversion=9.14.3.15
  39. Affected versionversion=9.14.3.18
  40. Affected versionversion=9.14.3.9
  41. Affected versionversion=9.14.4
  42. Affected versionversion=9.14.4.12
  43. Affected versionversion=9.14.4.13
  44. Affected versionversion=9.14.4.14
  45. Affected versionversion=9.14.4.15
  46. Affected versionversion=9.14.4.17
  47. Affected versionversion=9.14.4.22
  48. Affected versionversion=9.14.4.23
  49. Affected versionversion=9.14.4.6
  50. Affected versionversion=9.14.4.7
  51. Affected versionversion=9.15.1
  52. Affected versionversion=9.15.1.1
  53. Affected versionversion=9.15.1.10
  54. Affected versionversion=9.15.1.15
  55. Affected versionversion=9.15.1.16
  56. Affected versionversion=9.15.1.17
  57. Affected versionversion=9.15.1.21
  58. Affected versionversion=9.15.1.7
  59. Affected versionversion=9.16.1
  60. Affected versionversion=9.16.1.28
  61. Affected versionversion=9.16.2
  62. Affected versionversion=9.16.2.11
  63. Affected versionversion=9.16.2.13
  64. Affected versionversion=9.16.2.14
  65. Affected versionversion=9.16.2.3
  66. Affected versionversion=9.16.2.7
  67. Affected versionversion=9.16.3
  68. Affected versionversion=9.16.3.14
  69. Affected versionversion=9.16.3.15
  70. Affected versionversion=9.16.3.19
  71. Affected versionversion=9.16.3.23
  72. Affected versionversion=9.16.3.3
  73. Affected versionversion=9.16.4
  74. Affected versionversion=9.16.4.14
  75. Affected versionversion=9.16.4.9
  76. Affected versionversion=9.17.1
  77. Affected versionversion=9.17.1.10
  78. Affected versionversion=9.17.1.11
  79. Affected versionversion=9.17.1.13
  80. Affected versionversion=9.17.1.15
  81. Affected versionversion=9.17.1.20
  82. Affected versionversion=9.17.1.30
  83. Affected versionversion=9.17.1.7
  84. Affected versionversion=9.17.1.9
  85. Affected versionversion=9.18.1
  86. Affected versionversion=9.18.1.3
  87. Affected versionversion=9.18.2
  88. Affected versionversion=9.18.2.5
  89. Affected versionversion=9.18.2.7
  90. Affected versionversion=9.18.2.8
  91. Affected versionversion=9.18.3
  92. Affected versionversion=9.19.1
  93. Affected versionversion=9.19.1.5
  94. Affected versionversion=9.8.4.22
  95. Affected versionversion=9.8.4.25
  96. Affected versionversion=9.8.4.26
  97. Affected versionversion=9.8.4.29
  98. Affected versionversion=9.8.4.32
  99. Affected versionversion=9.8.4.33
  100. Affected versionversion=9.8.4.34
  101. Affected versionversion=9.8.4.35
  102. Affected versionversion=9.8.4.39
  103. Affected versionversion=9.8.4.40
  104. Affected versionversion=9.8.4.41
  105. Affected versionversion=9.8.4.43
  106. Affected versionversion=9.8.4.44
  107. Affected versionversion=9.8.4.45
  108. Affected versionversion=9.8.4.46
  109. Affected versionversion=9.8.4.48

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

ClamAV · Cisco Adaptive Security Appliance (ASA) Softwareversion=9.12.4.10; version=9.12.4.13; version=9.12.4.18; version=9.12.4.2; version=9.12.4.24; version=9.12.4.26; version=9.12.4.29; version=9.12.4.30; version=9.12.4.35; version=9.12.4.37; version=9.12.4.38; version=9.12.4.39; version=9.12.4.4; version=9.12.4.40; version=9.12.4.41; version=9.12.4.47; version=9.12.4.48; version=9.12.4.50; version=9.12.4.52; version=9.12.4.54; version=9.12.4.55; version=9.12.4.56; version=9.12.4.7; version=9.12.4.8; version=9.14.1.10; version=9.14.1.15; version=9.14.1.19; version=9.14.1.30; version=9.14.2; version=9.14.2.13; version=9.14.2.15; version=9.14.2.4; version=9.14.2.8; version=9.14.3; version=9.14.3.1; version=9.14.3.11; version=9.14.3.13; version=9.14.3.15; version=9.14.3.18; version=9.14.3.9; version=9.14.4; version=9.14.4.12; version=9.14.4.13; version=9.14.4.14; version=9.14.4.15; version=9.14.4.17; version=9.14.4.22; version=9.14.4.23; version=9.14.4.6; version=9.14.4.7; version=9.15.1; version=9.15.1.1; version=9.15.1.10; version=9.15.1.15; version=9.15.1.16; version=9.15.1.17; version=9.15.1.21; version=9.15.1.7; version=9.16.1; version=9.16.1.28; version=9.16.2; version=9.16.2.11; version=9.16.2.13; version=9.16.2.14; version=9.16.2.3; version=9.16.2.7; version=9.16.3; version=9.16.3.14; version=9.16.3.15; version=9.16.3.19; version=9.16.3.23; version=9.16.3.3; version=9.16.4; version=9.16.4.14; version=9.16.4.9; version=9.17.1; version=9.17.1.10; version=9.17.1.11; version=9.17.1.13; version=9.17.1.15; version=9.17.1.20; version=9.17.1.30; version=9.17.1.7; version=9.17.1.9; version=9.18.1; version=9.18.1.3; version=9.18.2; version=9.18.2.5; version=9.18.2.7; version=9.18.2.8; version=9.18.3; version=9.19.1; version=9.19.1.5; version=9.8.4.22; version=9.8.4.25; version=9.8.4.26; version=9.8.4.29; version=9.8.4.32; version=9.8.4.33; version=9.8.4.34; version=9.8.4.35; version=9.8.4.39; version=9.8.4.40; version=9.8.4.41; version=9.8.4.43; version=9.8.4.44; version=9.8.4.45; version=9.8.4.46; version=9.8.4.48
ClamAV · Cisco Firepower Threat Defenseversion=6.2.3.16; version=6.2.3.17; version=6.2.3.18; 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=6.6.1; 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=7.1.0.2; 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

5.0Cisco Systems, Inc.CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:N/I:L/A:N
5.8NIST NVDCVSS: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 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-290Authentication Bypass by Spoofing
T1190Exploit Public-Facing Application

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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