CVE-2024-20353Known exploitationNetwork attack vector

Unauthenticated device reload via malformed HTTP header

Published Apr 24, 2024 · Updated Oct 21, 2025

Denial of service in Cisco ASA and FTD management and VPN web servers allows remote attackers to reload devices via crafted HTTP requests. Their HTTP-header parser performs incomplete error checking and enters an infinite loop when it processes the crafted header. Exposure requires an SSL listening socket enabled by a management, HTTP, REST API, or remote-access VPN configuration, and exploitation interrupts service by rebooting the device.

CVSS severity8.6
High
EPSS probability70.69%
Next 30 days · Sep 16, 2026
Known exploitationReported
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Denial of service in Cisco ASA and FTD management and VPN web servers allows remote attackers to reload devices via crafted HTTP requests. Their HTTP-header parser performs incomplete error checking and enters an infinite loop when it processes the crafted header. Exposure requires an SSL listening socket enabled by a management, HTTP, REST API, or remote-access VPN configuration, and exploitation interrupts service by rebooting the device.

The record

CVE
CVE-2024-20353
Published
Apr 24, 2024
Updated
Oct 21, 2025
Vendor
ClamAV
Product
Cisco Adaptive Security Appliance (ASA) Software
Classifications
CWE-835, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Apr 24, 2024Exploitation reportedCISA Known Exploited Vulnerabilities Catalog entry
  2. Apr 24, 2024CVE publishedPublication date reported by the CVE source.
  3. Oct 21, 2025Record 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=9.12.1 <=9.12.4.65
  5. Affected versionversion=9.12.2
  6. Affected versionversion=9.12.2.1
  7. Affected versionversion=9.12.2.4
  8. Affected versionversion=9.12.2.5
  9. Affected versionversion=9.12.2.9
  10. Affected versionversion=9.12.3
  11. Affected versionversion=9.12.3.12
  12. Affected versionversion=9.12.3.2
  13. Affected versionversion=9.12.3.7
  14. Affected versionversion=9.12.3.9
  15. Affected versionversion=9.12.4
  16. Affected versionversion=9.12.4.10
  17. Affected versionversion=9.12.4.13
  18. Affected versionversion=9.12.4.18
  19. Affected versionversion=9.12.4.2
  20. Affected versionversion=9.12.4.24
  21. Affected versionversion=9.12.4.26
  22. Affected versionversion=9.12.4.29
  23. Affected versionversion=9.12.4.30
  24. Affected versionversion=9.12.4.35
  25. Affected versionversion=9.12.4.37
  26. Affected versionversion=9.12.4.38
  27. Affected versionversion=9.12.4.39
  28. Affected versionversion=9.12.4.4
  29. Affected versionversion=9.12.4.40
  30. Affected versionversion=9.12.4.41
  31. Affected versionversion=9.12.4.47
  32. Affected versionversion=9.12.4.48
  33. Affected versionversion=9.12.4.50
  34. Affected versionversion=9.12.4.52
  35. Affected versionversion=9.12.4.54
  36. Affected versionversion=9.12.4.55
  37. Affected versionversion=9.12.4.56
  38. Affected versionversion=9.12.4.58
  39. Affected versionversion=9.12.4.62
  40. Affected versionversion=9.12.4.65
  41. Affected versionversion=9.12.4.7
  42. Affected versionversion=9.12.4.8
  43. Affected versionversion=9.14.1
  44. Affected versionversion=9.14.1.10
  45. Affected versionversion=9.14.1.15
  46. Affected versionversion=9.14.1.19
  47. Affected versionversion=9.14.1.30
  48. Affected versionversion=9.14.1.6
  49. Affected versionversion=9.14.1 <9.14.4.23
  50. Affected versionversion=9.14.2
  51. Affected versionversion=9.14.2.13
  52. Affected versionversion=9.14.2.15
  53. Affected versionversion=9.14.2.4
  54. Affected versionversion=9.14.2.8
  55. Affected versionversion=9.14.3
  56. Affected versionversion=9.14.3.1
  57. Affected versionversion=9.14.3.11
  58. Affected versionversion=9.14.3.13
  59. Affected versionversion=9.14.3.15
  60. Affected versionversion=9.14.3.18
  61. Affected versionversion=9.14.3.9
  62. Affected versionversion=9.14.4
  63. Affected versionversion=9.14.4.12
  64. Affected versionversion=9.14.4.13
  65. Affected versionversion=9.14.4.14
  66. Affected versionversion=9.14.4.15
  67. Affected versionversion=9.14.4.17
  68. Affected versionversion=9.14.4.22
  69. Affected versionversion=9.14.4.23
  70. Affected versionversion=9.14.4.6
  71. Affected versionversion=9.14.4.7
  72. Affected versionversion=9.15.1
  73. Affected versionversion=9.15.1.1
  74. Affected versionversion=9.15.1.10
  75. Affected versionversion=9.15.1.15
  76. Affected versionversion=9.15.1.16
  77. Affected versionversion=9.15.1.17
  78. Affected versionversion=9.15.1.21
  79. Affected versionversion=9.15.1.7
  80. Affected versionversion=9.15.1 <=9.15.1.21
  81. Affected versionversion=9.16.1
  82. Affected versionversion=9.16.1.28
  83. Affected versionversion=9.16.1 <=9.16.4.55
  84. Affected versionversion=9.16.2
  85. Affected versionversion=9.16.2.11
  86. Affected versionversion=9.16.2.13
  87. Affected versionversion=9.16.2.14
  88. Affected versionversion=9.16.2.3
  89. Affected versionversion=9.16.2.7
  90. Affected versionversion=9.16.3
  91. Affected versionversion=9.16.3.14
  92. Affected versionversion=9.16.3.15
  93. Affected versionversion=9.16.3.19
  94. Affected versionversion=9.16.3.23
  95. Affected versionversion=9.16.3.3
  96. Affected versionversion=9.16.4
  97. Affected versionversion=9.16.4.14
  98. Affected versionversion=9.16.4.18
  99. Affected versionversion=9.16.4.19
  100. Affected versionversion=9.16.4.27
  101. Affected versionversion=9.16.4.38
  102. Affected versionversion=9.16.4.39
  103. Affected versionversion=9.16.4.42
  104. Affected versionversion=9.16.4.48
  105. Affected versionversion=9.16.4.55
  106. Affected versionversion=9.16.4.9
  107. Affected versionversion=9.17.1
  108. Affected versionversion=9.17.1.10
  109. Affected versionversion=9.17.1.11
  110. Affected versionversion=9.17.1.13
  111. Affected versionversion=9.17.1.15
  112. Affected versionversion=9.17.1.20
  113. Affected versionversion=9.17.1.30
  114. Affected versionversion=9.17.1.33
  115. Affected versionversion=9.17.1.7
  116. Affected versionversion=9.17.1.9
  117. Affected versionversion=9.17.1 <=9.17.1.33
  118. Affected versionversion=9.18.1
  119. Affected versionversion=9.18.1.3
  120. Affected versionversion=9.18.1 <=9.18.4.8
  121. Affected versionversion=9.18.2
  122. Affected versionversion=9.18.2.5
  123. Affected versionversion=9.18.2.7
  124. Affected versionversion=9.18.2.8
  125. Affected versionversion=9.18.3
  126. Affected versionversion=9.18.3.39
  127. Affected versionversion=9.18.3.46
  128. Affected versionversion=9.18.3.53
  129. Affected versionversion=9.18.3.55
  130. Affected versionversion=9.18.3.56
  131. Affected versionversion=9.18.4
  132. Affected versionversion=9.18.4.5
  133. Affected versionversion=9.18.4.8
  134. Affected versionversion=9.19.1
  135. Affected versionversion=9.19.1.12
  136. Affected versionversion=9.19.1.18
  137. Affected versionversion=9.19.1.22
  138. Affected versionversion=9.19.1.24
  139. Affected versionversion=9.19.1.27
  140. Affected versionversion=9.19.1.5
  141. Affected versionversion=9.19.1.9
  142. Affected versionversion=9.19.1 <=9.19.1.27
  143. Affected versionversion=9.20.1
  144. Affected versionversion=9.20.1.5
  145. Affected versionversion=9.20.1 <=9.20.2
  146. Affected versionversion=9.20.2
  147. Affected versionversion=9.8.1
  148. Affected versionversion=9.8.1.5
  149. Affected versionversion=9.8.1.7
  150. Affected versionversion=9.8.1 <=9.8.4.48
  151. Affected versionversion=9.8.2
  152. Affected versionversion=9.8.2.14
  153. Affected versionversion=9.8.2.15
  154. Affected versionversion=9.8.2.17
  155. Affected versionversion=9.8.2.20
  156. Affected versionversion=9.8.2.24
  157. Affected versionversion=9.8.2.26
  158. Affected versionversion=9.8.2.28
  159. Affected versionversion=9.8.2.33
  160. Affected versionversion=9.8.2.35
  161. Affected versionversion=9.8.2.38
  162. Affected versionversion=9.8.2.8
  163. Affected versionversion=9.8.3
  164. Affected versionversion=9.8.3.11
  165. Affected versionversion=9.8.3.14
  166. Affected versionversion=9.8.3.16
  167. Affected versionversion=9.8.3.18
  168. Affected versionversion=9.8.3.21
  169. Affected versionversion=9.8.3.26
  170. Affected versionversion=9.8.3.29
  171. Affected versionversion=9.8.3.8
  172. Affected versionversion=9.8.4
  173. Affected versionversion=9.8.4.10
  174. Affected versionversion=9.8.4.12
  175. Affected versionversion=9.8.4.15
  176. Affected versionversion=9.8.4.17
  177. Affected versionversion=9.8.4.20
  178. Affected versionversion=9.8.4.22
  179. Affected versionversion=9.8.4.25
  180. Affected versionversion=9.8.4.26
  181. Affected versionversion=9.8.4.29
  182. Affected versionversion=9.8.4.3
  183. Affected versionversion=9.8.4.32
  184. Affected versionversion=9.8.4.33
  185. Affected versionversion=9.8.4.34
  186. Affected versionversion=9.8.4.35
  187. Affected versionversion=9.8.4.39
  188. Affected versionversion=9.8.4.40
  189. Affected versionversion=9.8.4.41
  190. Affected versionversion=9.8.4.43
  191. Affected versionversion=9.8.4.44
  192. Affected versionversion=9.8.4.45
  193. Affected versionversion=9.8.4.46
  194. Affected versionversion=9.8.4.48
  195. Affected versionversion=9.8.4.7
  196. Affected versionversion=9.8.4.8

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=9.12.1 <=9.12.4.65; 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=9.12.4.7; version=9.12.4.8; version=9.14.1; version=9.14.1.10; version=9.14.1.15; version=9.14.1.19; version=9.14.1.30; version=9.14.1.6; version=9.14.1 <9.14.4.23; 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=9.15.1 <=9.15.1.21; version=9.16.1; version=9.16.1.28; version=9.16.1 <=9.16.4.55; 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=9.16.4.18; 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=9.16.4.9; 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=9.17.1.7; version=9.17.1.9; version=9.17.1 <=9.17.1.33; version=9.18.1; version=9.18.1.3; version=9.18.1 <=9.18.4.8; 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=9.18.4.5; 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=9.19.1.5; version=9.19.1.9; version=9.19.1 <=9.19.1.27; version=9.20.1; version=9.20.1.5; version=9.20.1 <=9.20.2; version=9.20.2; version=9.8.1; version=9.8.1.5; version=9.8.1.7; version=9.8.1 <=9.8.4.48; version=9.8.2; version=9.8.2.14; version=9.8.2.15; version=9.8.2.17; version=9.8.2.20; version=9.8.2.24; version=9.8.2.26; version=9.8.2.28; version=9.8.2.33; version=9.8.2.35; version=9.8.2.38; version=9.8.2.8; version=9.8.3; version=9.8.3.11; version=9.8.3.14; version=9.8.3.16; version=9.8.3.18; version=9.8.3.21; version=9.8.3.26; version=9.8.3.29; version=9.8.3.8; version=9.8.4; version=9.8.4.10; version=9.8.4.12; version=9.8.4.15; version=9.8.4.17; version=9.8.4.20; version=9.8.4.22; version=9.8.4.25; version=9.8.4.26; version=9.8.4.29; version=9.8.4.3; 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; version=9.8.4.7; version=9.8.4.8
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 <=6.2.3.18; 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=6.4.0.17; 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 <=6.4.0.17; 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=6.6.0 <=6.6.7.1; 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=6.7.0 <=6.7.0.3; version=7.0.0; version=7.0.0.1; version=7.0.0 <=7.0.6; 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=7.1.0; version=7.1.0.1; version=7.1.0.2; version=7.1.0.3; version=7.1.0 <=7.1.0.3; version=7.2.0; version=7.2.0.1; version=7.2.0 <=7.2.4.1; 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=7.3.0; version=7.3.0 <=7.3.1.1; version=7.3.1; version=7.3.1.1; version=7.4.0; version=7.4.0 <=7.4.1; version=7.4.1

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 exploitationReported
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-835Loop with Unreachable Exit Condition ('Infinite Loop')
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.

Reported exploitation

Technologies

Your stack

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Your stack

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