CVE-2026-20021

Denial of service via OSPF memory exhaustion

Published Mar 4, 2026 · Updated Mar 4, 2026

Denial of service in Cisco Secure Firewall ASA and Secure FTD Software allows attackers to exhaust device memory through OSPF packets. The OSPF packet parser insufficiently validates crafted protocol input and retains memory until available device memory is depleted. Exploitation requires adjacency to an affected device running OSPF but requires no authentication; the resulting resource exhaustion interrupts service.

CVSS severity4.3
Medium
EPSS probability0.20%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Denial of service in Cisco Secure Firewall ASA and Secure FTD Software allows attackers to exhaust device memory through OSPF packets. The OSPF packet parser insufficiently validates crafted protocol input and retains memory until available device memory is depleted. Exploitation requires adjacency to an affected device running OSPF but requires no authentication; the resulting resource exhaustion interrupts service.

The record

CVE
CVE-2026-20021
Published
Mar 4, 2026
Updated
Mar 4, 2026
Vendor
ClamAV
Product
Cisco Adaptive Security Appliance (ASA) Software
Classifications
CWE-401, T1499.002
Attack vector
adjacent
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=9.16.4.84
  75. Affected versionversion=9.16.4.85
  76. Affected versionversion=9.16.4.9
  77. Affected versionversion=9.17.1
  78. Affected versionversion=9.17.1.10
  79. Affected versionversion=9.17.1.11
  80. Affected versionversion=9.17.1.13
  81. Affected versionversion=9.17.1.15
  82. Affected versionversion=9.17.1.20
  83. Affected versionversion=9.17.1.30
  84. Affected versionversion=9.17.1.33
  85. Affected versionversion=9.17.1.39
  86. Affected versionversion=9.17.1.45
  87. Affected versionversion=9.17.1.46
  88. Affected versionversion=9.17.1.7
  89. Affected versionversion=9.17.1.9
  90. Affected versionversion=9.18.1
  91. Affected versionversion=9.18.1.3
  92. Affected versionversion=9.18.2
  93. Affected versionversion=9.18.2.5
  94. Affected versionversion=9.18.2.7
  95. Affected versionversion=9.18.2.8
  96. Affected versionversion=9.18.3
  97. Affected versionversion=9.18.3.39
  98. Affected versionversion=9.18.3.46
  99. Affected versionversion=9.18.3.53
  100. Affected versionversion=9.18.3.55
  101. Affected versionversion=9.18.3.56
  102. Affected versionversion=9.18.4
  103. Affected versionversion=9.18.4.22
  104. Affected versionversion=9.18.4.24
  105. Affected versionversion=9.18.4.29
  106. Affected versionversion=9.18.4.34
  107. Affected versionversion=9.18.4.40
  108. Affected versionversion=9.18.4.47
  109. Affected versionversion=9.18.4.5
  110. Affected versionversion=9.18.4.50
  111. Affected versionversion=9.18.4.52
  112. Affected versionversion=9.18.4.53
  113. Affected versionversion=9.18.4.57
  114. Affected versionversion=9.18.4.66
  115. Affected versionversion=9.18.4.67
  116. Affected versionversion=9.18.4.68
  117. Affected versionversion=9.18.4.8
  118. Affected versionversion=9.19.1
  119. Affected versionversion=9.19.1.12
  120. Affected versionversion=9.19.1.18
  121. Affected versionversion=9.19.1.22
  122. Affected versionversion=9.19.1.24
  123. Affected versionversion=9.19.1.27
  124. Affected versionversion=9.19.1.28
  125. Affected versionversion=9.19.1.31
  126. Affected versionversion=9.19.1.37
  127. Affected versionversion=9.19.1.38
  128. Affected versionversion=9.19.1.42
  129. Affected versionversion=9.19.1.5
  130. Affected versionversion=9.19.1.9
  131. Affected versionversion=9.20.1
  132. Affected versionversion=9.20.1.5
  133. Affected versionversion=9.20.2
  134. Affected versionversion=9.20.2.10
  135. Affected versionversion=9.20.2.21
  136. Affected versionversion=9.20.2.22
  137. Affected versionversion=9.20.3
  138. Affected versionversion=9.20.3.10
  139. Affected versionversion=9.20.3.13
  140. Affected versionversion=9.20.3.16
  141. Affected versionversion=9.20.3.20
  142. Affected versionversion=9.20.3.4
  143. Affected versionversion=9.20.3.7
  144. Affected versionversion=9.20.3.9
  145. Affected versionversion=9.20.4
  146. Affected versionversion=9.20.4.10
  147. Affected versionversion=9.20.4.14
  148. Affected versionversion=9.20.4.7
  149. Affected versionversion=9.22.1.1
  150. Affected versionversion=9.22.1.2
  151. Affected versionversion=9.22.1.3
  152. Affected versionversion=9.22.1.6
  153. Affected versionversion=9.22.2
  154. Affected versionversion=9.22.2.13
  155. Affected versionversion=9.22.2.14
  156. Affected versionversion=9.22.2.4
  157. Affected versionversion=9.22.2.9
  158. Affected versionversion=9.23.1
  159. Affected versionversion=9.23.1.13
  160. Affected versionversion=9.23.1.19
  161. Affected versionversion=9.23.1.22
  162. Affected versionversion=9.23.1.3
  163. Affected versionversion=9.23.1.7

What conditions does exploitation require?

Attack vectoradjacent
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=9.16.4.84; version=9.16.4.85; 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=9.18.4.57; version=9.18.4.66; version=9.18.4.67; version=9.18.4.68; 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=9.20.3.16; version=9.20.3.20; version=9.20.3.4; version=9.20.3.7; version=9.20.3.9; version=9.20.4; version=9.20.4.10; version=9.20.4.14; version=9.20.4.7; 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=9.22.2.13; version=9.22.2.14; version=9.22.2.4; version=9.22.2.9; version=9.23.1; version=9.23.1.13; version=9.23.1.19; version=9.23.1.22; version=9.23.1.3; version=9.23.1.7
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=7.2.10; version=7.2.10.2; 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=7.4.3; version=7.6.0; version=7.6.1; version=7.6.2; version=7.6.2.1; version=7.7.0; version=7.7.10; version=7.7.10.1

Published CVSS scores

4.3Cisco Systems, Inc.CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

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)
Vectoradjacent
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-401Missing Release of Memory after Effective Lifetime
T1499.002Service 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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