CVE-2026-20039Network attack vector

Device reload via crafted VPN HTTP request flood

Published Mar 4, 2026 · Updated Mar 4, 2026

VPN web server denial of service in Cisco ASA and FTD Software allows remote attackers to reload affected devices with crafted HTTP floods. The VPN web server manages memory ineffectively while processing a large volume of crafted HTTP requests. Exposure requires SSL VPN or IKEv2 Remote Access VPN with client services; successful exploitation reloads the device and interrupts service.

CVSS severity8.6
High
EPSS probability0.36%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

VPN web server denial of service in Cisco ASA and FTD Software allows remote attackers to reload affected devices with crafted HTTP floods. The VPN web server manages memory ineffectively while processing a large volume of crafted HTTP requests. Exposure requires SSL VPN or IKEv2 Remote Access VPN with client services; successful exploitation reloads the device and interrupts service.

The record

CVE
CVE-2026-20039
Published
Mar 4, 2026
Updated
Mar 4, 2026
Vendor
ClamAV
Product
Cisco Adaptive Security Appliance (ASA) Software
Classifications
CWE-244, T1499.003
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Mar 4, 2026CVE publishedPublication date reported by the CVE source.
  2. Mar 4, 2026Record 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=9.12.1
  2. Affected versionversion=9.12.1.2
  3. Affected versionversion=9.12.1.3
  4. Affected versionversion=9.12.2
  5. Affected versionversion=9.12.2.1
  6. Affected versionversion=9.12.2.4
  7. Affected versionversion=9.12.2.5
  8. Affected versionversion=9.12.2.9
  9. Affected versionversion=9.12.3
  10. Affected versionversion=9.12.3.12
  11. Affected versionversion=9.12.3.2
  12. Affected versionversion=9.12.3.7
  13. Affected versionversion=9.12.3.9
  14. Affected versionversion=9.12.4
  15. Affected versionversion=9.12.4.10
  16. Affected versionversion=9.12.4.13
  17. Affected versionversion=9.12.4.18
  18. Affected versionversion=9.12.4.2
  19. Affected versionversion=9.12.4.24
  20. Affected versionversion=9.12.4.26
  21. Affected versionversion=9.12.4.29
  22. Affected versionversion=9.12.4.30
  23. Affected versionversion=9.12.4.35
  24. Affected versionversion=9.12.4.37
  25. Affected versionversion=9.12.4.38
  26. Affected versionversion=9.12.4.39
  27. Affected versionversion=9.12.4.4
  28. Affected versionversion=9.12.4.40
  29. Affected versionversion=9.12.4.41
  30. Affected versionversion=9.12.4.47
  31. Affected versionversion=9.12.4.48
  32. Affected versionversion=9.12.4.50
  33. Affected versionversion=9.12.4.52
  34. Affected versionversion=9.12.4.54
  35. Affected versionversion=9.12.4.55
  36. Affected versionversion=9.12.4.56
  37. Affected versionversion=9.12.4.58
  38. Affected versionversion=9.12.4.62
  39. Affected versionversion=9.12.4.65
  40. Affected versionversion=9.12.4.67
  41. Affected versionversion=9.12.4.7
  42. Affected versionversion=9.12.4.8
  43. Affected versionversion=9.16.1
  44. Affected versionversion=9.16.1.28
  45. Affected versionversion=9.16.2
  46. Affected versionversion=9.16.2.11
  47. Affected versionversion=9.16.2.13
  48. Affected versionversion=9.16.2.14
  49. Affected versionversion=9.16.2.3
  50. Affected versionversion=9.16.2.7
  51. Affected versionversion=9.16.3
  52. Affected versionversion=9.16.3.14
  53. Affected versionversion=9.16.3.15
  54. Affected versionversion=9.16.3.19
  55. Affected versionversion=9.16.3.23
  56. Affected versionversion=9.16.3.3
  57. Affected versionversion=9.16.4
  58. Affected versionversion=9.16.4.14
  59. Affected versionversion=9.16.4.19
  60. Affected versionversion=9.16.4.27
  61. Affected versionversion=9.16.4.38
  62. Affected versionversion=9.16.4.39
  63. Affected versionversion=9.16.4.42
  64. Affected versionversion=9.16.4.48
  65. Affected versionversion=9.16.4.55
  66. Affected versionversion=9.16.4.57
  67. Affected versionversion=9.16.4.61
  68. Affected versionversion=9.16.4.62
  69. Affected versionversion=9.16.4.67
  70. Affected versionversion=9.16.4.70
  71. Affected versionversion=9.16.4.71
  72. Affected versionversion=9.16.4.76
  73. Affected versionversion=9.16.4.82
  74. Affected versionversion=9.16.4.9
  75. Affected versionversion=9.17.1
  76. Affected versionversion=9.17.1.10
  77. Affected versionversion=9.17.1.11
  78. Affected versionversion=9.17.1.13
  79. Affected versionversion=9.17.1.15
  80. Affected versionversion=9.17.1.20
  81. Affected versionversion=9.17.1.30
  82. Affected versionversion=9.17.1.33
  83. Affected versionversion=9.17.1.39
  84. Affected versionversion=9.17.1.45
  85. Affected versionversion=9.17.1.46
  86. Affected versionversion=9.17.1.7
  87. Affected versionversion=9.17.1.9
  88. Affected versionversion=9.18.1
  89. Affected versionversion=9.18.1.3
  90. Affected versionversion=9.18.2
  91. Affected versionversion=9.18.2.5
  92. Affected versionversion=9.18.2.7
  93. Affected versionversion=9.18.2.8
  94. Affected versionversion=9.18.3
  95. Affected versionversion=9.18.3.39
  96. Affected versionversion=9.18.3.46
  97. Affected versionversion=9.18.3.53
  98. Affected versionversion=9.18.3.55
  99. Affected versionversion=9.18.3.56
  100. Affected versionversion=9.18.4
  101. Affected versionversion=9.18.4.22
  102. Affected versionversion=9.18.4.24
  103. Affected versionversion=9.18.4.29
  104. Affected versionversion=9.18.4.34
  105. Affected versionversion=9.18.4.40
  106. Affected versionversion=9.18.4.47
  107. Affected versionversion=9.18.4.5
  108. Affected versionversion=9.18.4.50
  109. Affected versionversion=9.18.4.52
  110. Affected versionversion=9.18.4.53
  111. Affected versionversion=9.18.4.8
  112. Affected versionversion=9.19.1
  113. Affected versionversion=9.19.1.12
  114. Affected versionversion=9.19.1.18
  115. Affected versionversion=9.19.1.22
  116. Affected versionversion=9.19.1.24
  117. Affected versionversion=9.19.1.27
  118. Affected versionversion=9.19.1.28
  119. Affected versionversion=9.19.1.31
  120. Affected versionversion=9.19.1.37
  121. Affected versionversion=9.19.1.38
  122. Affected versionversion=9.19.1.42
  123. Affected versionversion=9.19.1.5
  124. Affected versionversion=9.19.1.9
  125. Affected versionversion=9.20.1
  126. Affected versionversion=9.20.1.5
  127. Affected versionversion=9.20.2
  128. Affected versionversion=9.20.2.10
  129. Affected versionversion=9.20.2.21
  130. Affected versionversion=9.20.2.22
  131. Affected versionversion=9.20.3
  132. Affected versionversion=9.20.3.10
  133. Affected versionversion=9.20.3.13
  134. Affected versionversion=9.20.3.4
  135. Affected versionversion=9.20.3.7
  136. Affected versionversion=9.20.3.9
  137. Affected versionversion=9.22.1.1
  138. Affected versionversion=9.22.1.2
  139. Affected versionversion=9.22.1.3
  140. Affected versionversion=9.22.1.6
  141. Affected versionversion=9.22.2
  142. Affected versionversion=9.23.1

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

ClamAV · Cisco Adaptive Security Appliance (ASA) Softwareversion=9.12.1; version=9.12.1.2; version=9.12.1.3; version=9.12.2; version=9.12.2.1; version=9.12.2.4; version=9.12.2.5; version=9.12.2.9; version=9.12.3; version=9.12.3.12; version=9.12.3.2; version=9.12.3.7; version=9.12.3.9; version=9.12.4; version=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=9.12.4.58; version=9.12.4.62; version=9.12.4.65; version=9.12.4.67; version=9.12.4.7; version=9.12.4.8; 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=9.16.4.19; version=9.16.4.27; version=9.16.4.38; version=9.16.4.39; version=9.16.4.42; version=9.16.4.48; version=9.16.4.55; version=9.16.4.57; version=9.16.4.61; version=9.16.4.62; version=9.16.4.67; version=9.16.4.70; version=9.16.4.71; version=9.16.4.76; version=9.16.4.82; 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=9.17.1.33; version=9.17.1.39; version=9.17.1.45; version=9.17.1.46; 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=9.18.3.39; version=9.18.3.46; version=9.18.3.53; version=9.18.3.55; version=9.18.3.56; version=9.18.4; version=9.18.4.22; version=9.18.4.24; version=9.18.4.29; version=9.18.4.34; version=9.18.4.40; version=9.18.4.47; version=9.18.4.5; version=9.18.4.50; version=9.18.4.52; version=9.18.4.53; version=9.18.4.8; version=9.19.1; version=9.19.1.12; version=9.19.1.18; version=9.19.1.22; version=9.19.1.24; version=9.19.1.27; version=9.19.1.28; version=9.19.1.31; version=9.19.1.37; version=9.19.1.38; version=9.19.1.42; version=9.19.1.5; version=9.19.1.9; version=9.20.1; version=9.20.1.5; version=9.20.2; version=9.20.2.10; version=9.20.2.21; version=9.20.2.22; version=9.20.3; version=9.20.3.10; version=9.20.3.13; version=9.20.3.4; version=9.20.3.7; version=9.20.3.9; version=9.22.1.1; version=9.22.1.2; version=9.22.1.3; version=9.22.1.6; version=9.22.2; version=9.23.1
ClamAV · Cisco Secure Firewall Threat Defenseversion=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=6.4.0.17; version=6.4.0.18; 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=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=7.0.6; version=7.0.6.1; version=7.0.6.2; version=7.0.6.3; version=7.0.7; version=7.0.8; version=7.0.8.1; 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=7.2.4; version=7.2.4.1; version=7.2.5; version=7.2.5.1; version=7.2.5.2; version=7.2.6; version=7.2.7; version=7.2.8; version=7.2.8.1; version=7.2.9; version=7.3.0; version=7.3.1; version=7.3.1.1; version=7.3.1.2; version=7.4.0; version=7.4.1; version=7.4.1.1; version=7.4.2; version=7.4.2.1; version=7.4.2.2; version=7.4.2.3; version=7.4.2.4; version=7.6.0; version=7.7.0

Published CVSS scores

8.6CiscoCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H/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 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-244Improper Clearing of Heap Memory Before Release ('Heap Inspection')
T1499.003Application Exhaustion Flood

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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