CVE-2023-20187Network attack vector

Router reload via mishandled IPv6 multicast fan-out

Published Sep 27, 2023 · Updated Aug 2, 2024

Denial of service in Cisco IOS XE Software on ASR 1000 routers allows remote attackers to reload affected devices with IPv6 multicast traffic. The mLRE feature incorrectly handles an IPv6 multicast or MVPNv6 packet when the packet fans out to more than seven interfaces. Exposure requires a specified ESP, IPv6 multicast routing with fan-out above seven, and mLRE, which is enabled by default on affected platforms; exploitation reloads the router and interrupts service.

CVSS severity8.6
High
EPSS probability0.65%
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 IOS XE Software on ASR 1000 routers allows remote attackers to reload affected devices with IPv6 multicast traffic. The mLRE feature incorrectly handles an IPv6 multicast or MVPNv6 packet when the packet fans out to more than seven interfaces. Exposure requires a specified ESP, IPv6 multicast routing with fan-out above seven, and mLRE, which is enabled by default on affected platforms; exploitation reloads the router and interrupts service.

The record

CVE
CVE-2023-20187
Published
Sep 27, 2023
Updated
Aug 2, 2024
Vendor
ClamAV
Product
Cisco IOS XE Software
Classifications
CWE-823, CAPEC-129, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Sep 27, 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=16.10.1
  2. Affected versionversion=16.10.1a
  3. Affected versionversion=16.10.1e
  4. Affected versionversion=16.10.1s
  5. Affected versionversion=16.10.2
  6. Affected versionversion=16.10.3
  7. Affected versionversion=16.11.1
  8. Affected versionversion=16.11.1a
  9. Affected versionversion=16.11.1s
  10. Affected versionversion=16.11.2
  11. Affected versionversion=16.12.1
  12. Affected versionversion=16.12.10a
  13. Affected versionversion=16.12.1a
  14. Affected versionversion=16.12.1c
  15. Affected versionversion=16.12.1s
  16. Affected versionversion=16.12.2
  17. Affected versionversion=16.12.2s
  18. Affected versionversion=16.12.3
  19. Affected versionversion=16.12.3s
  20. Affected versionversion=16.12.4
  21. Affected versionversion=16.12.5
  22. Affected versionversion=16.12.6
  23. Affected versionversion=16.12.7
  24. Affected versionversion=16.12.8
  25. Affected versionversion=16.2.1
  26. Affected versionversion=16.2.2
  27. Affected versionversion=16.3.1
  28. Affected versionversion=16.3.10
  29. Affected versionversion=16.3.11
  30. Affected versionversion=16.3.1a
  31. Affected versionversion=16.3.2
  32. Affected versionversion=16.3.3
  33. Affected versionversion=16.3.4
  34. Affected versionversion=16.3.5
  35. Affected versionversion=16.3.6
  36. Affected versionversion=16.3.7
  37. Affected versionversion=16.3.8
  38. Affected versionversion=16.3.9
  39. Affected versionversion=16.4.1
  40. Affected versionversion=16.4.2
  41. Affected versionversion=16.4.3
  42. Affected versionversion=16.5.1
  43. Affected versionversion=16.5.1b
  44. Affected versionversion=16.5.2
  45. Affected versionversion=16.5.3
  46. Affected versionversion=16.6.1
  47. Affected versionversion=16.6.10
  48. Affected versionversion=16.6.2
  49. Affected versionversion=16.6.3
  50. Affected versionversion=16.6.4
  51. Affected versionversion=16.6.5
  52. Affected versionversion=16.6.6
  53. Affected versionversion=16.6.7
  54. Affected versionversion=16.6.8
  55. Affected versionversion=16.6.9
  56. Affected versionversion=16.7.1
  57. Affected versionversion=16.7.2
  58. Affected versionversion=16.7.3
  59. Affected versionversion=16.8.1
  60. Affected versionversion=16.8.1s
  61. Affected versionversion=16.8.2
  62. Affected versionversion=16.8.3
  63. Affected versionversion=16.9.1
  64. Affected versionversion=16.9.1s
  65. Affected versionversion=16.9.2
  66. Affected versionversion=16.9.3
  67. Affected versionversion=16.9.4
  68. Affected versionversion=16.9.5
  69. Affected versionversion=16.9.6
  70. Affected versionversion=16.9.7
  71. Affected versionversion=16.9.8
  72. Affected versionversion=17.10.1
  73. Affected versionversion=17.10.1a
  74. Affected versionversion=17.1.1
  75. Affected versionversion=17.11.1
  76. Affected versionversion=17.11.1a
  77. Affected versionversion=17.1.1s
  78. Affected versionversion=17.1.1t
  79. Affected versionversion=17.1.3
  80. Affected versionversion=17.2.1
  81. Affected versionversion=17.2.1r
  82. Affected versionversion=17.2.1v
  83. Affected versionversion=17.2.2
  84. Affected versionversion=17.2.3
  85. Affected versionversion=17.3.1
  86. Affected versionversion=17.3.1a
  87. Affected versionversion=17.3.2
  88. Affected versionversion=17.3.3
  89. Affected versionversion=17.3.4
  90. Affected versionversion=17.3.4a
  91. Affected versionversion=17.3.5
  92. Affected versionversion=17.3.6
  93. Affected versionversion=17.3.7
  94. Affected versionversion=17.4.1
  95. Affected versionversion=17.4.1a
  96. Affected versionversion=17.4.1b
  97. Affected versionversion=17.4.2
  98. Affected versionversion=17.5.1
  99. Affected versionversion=17.5.1a
  100. Affected versionversion=17.5.1b
  101. Affected versionversion=17.5.1c
  102. Affected versionversion=17.6.1
  103. Affected versionversion=17.6.1a
  104. Affected versionversion=17.6.2
  105. Affected versionversion=17.6.3
  106. Affected versionversion=17.6.3a
  107. Affected versionversion=17.6.4
  108. Affected versionversion=17.6.5
  109. Affected versionversion=17.6.5a
  110. Affected versionversion=17.7.1
  111. Affected versionversion=17.7.1a
  112. Affected versionversion=17.7.2
  113. Affected versionversion=17.8.1
  114. Affected versionversion=17.8.1a
  115. Affected versionversion=17.9.1
  116. Affected versionversion=17.9.1a
  117. Affected versionversion=17.9.2
  118. Affected versionversion=17.9.2a
  119. Affected versionversion=17.9.3
  120. Affected versionversion=17.9.3a
  121. Affected versionversion=3.10.0S
  122. Affected versionversion=3.10.10S
  123. Affected versionversion=3.10.1S
  124. Affected versionversion=3.10.1xbS
  125. Affected versionversion=3.10.2S
  126. Affected versionversion=3.10.3S
  127. Affected versionversion=3.10.4S
  128. Affected versionversion=3.10.5S
  129. Affected versionversion=3.10.6S
  130. Affected versionversion=3.10.7S
  131. Affected versionversion=3.10.8aS
  132. Affected versionversion=3.10.8S
  133. Affected versionversion=3.10.9S
  134. Affected versionversion=3.11.0S
  135. Affected versionversion=3.11.1S
  136. Affected versionversion=3.11.2S
  137. Affected versionversion=3.11.3S
  138. Affected versionversion=3.11.4S
  139. Affected versionversion=3.12.0S
  140. Affected versionversion=3.12.1S
  141. Affected versionversion=3.12.2S
  142. Affected versionversion=3.12.3S
  143. Affected versionversion=3.12.4S
  144. Affected versionversion=3.13.0S
  145. Affected versionversion=3.13.10S
  146. Affected versionversion=3.13.1S
  147. Affected versionversion=3.13.2aS
  148. Affected versionversion=3.13.2S
  149. Affected versionversion=3.13.3S
  150. Affected versionversion=3.13.4S
  151. Affected versionversion=3.13.5aS
  152. Affected versionversion=3.13.5S
  153. Affected versionversion=3.13.6aS
  154. Affected versionversion=3.13.6S
  155. Affected versionversion=3.13.7S
  156. Affected versionversion=3.13.8S
  157. Affected versionversion=3.13.9S
  158. Affected versionversion=3.14.0S
  159. Affected versionversion=3.14.1S
  160. Affected versionversion=3.14.2S
  161. Affected versionversion=3.14.3S
  162. Affected versionversion=3.14.4S
  163. Affected versionversion=3.15.0S
  164. Affected versionversion=3.15.1S
  165. Affected versionversion=3.15.2S
  166. Affected versionversion=3.15.3S
  167. Affected versionversion=3.15.4S
  168. Affected versionversion=3.16.0S
  169. Affected versionversion=3.16.10S
  170. Affected versionversion=3.16.1aS
  171. Affected versionversion=3.16.2bS
  172. Affected versionversion=3.16.2S
  173. Affected versionversion=3.16.3S
  174. Affected versionversion=3.16.4aS
  175. Affected versionversion=3.16.4bS
  176. Affected versionversion=3.16.5S
  177. Affected versionversion=3.16.6bS
  178. Affected versionversion=3.16.6S
  179. Affected versionversion=3.16.7aS
  180. Affected versionversion=3.16.7bS
  181. Affected versionversion=3.16.7S
  182. Affected versionversion=3.16.8S
  183. Affected versionversion=3.16.9S
  184. Affected versionversion=3.17.0S
  185. Affected versionversion=3.17.1aS
  186. Affected versionversion=3.17.1S
  187. Affected versionversion=3.17.2S
  188. Affected versionversion=3.17.3S
  189. Affected versionversion=3.17.4S
  190. Affected versionversion=3.7.1S
  191. Affected versionversion=3.7.2S
  192. Affected versionversion=3.7.2tS
  193. Affected versionversion=3.7.3S
  194. Affected versionversion=3.7.4S
  195. Affected versionversion=3.7.5S
  196. Affected versionversion=3.7.6S
  197. Affected versionversion=3.7.7S
  198. Affected versionversion=3.8.0S
  199. Affected versionversion=3.8.1S
  200. Affected versionversion=3.8.2S
  201. Affected versionversion=3.9.0S
  202. Affected versionversion=3.9.1S
  203. Affected versionversion=3.9.2S

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

ClamAV · Cisco IOS XE Softwareversion=16.10.1; version=16.10.1a; version=16.10.1e; version=16.10.1s; version=16.10.2; version=16.10.3; version=16.11.1; version=16.11.1a; version=16.11.1s; version=16.11.2; version=16.12.1; version=16.12.10a; version=16.12.1a; version=16.12.1c; version=16.12.1s; version=16.12.2; version=16.12.2s; version=16.12.3; version=16.12.3s; version=16.12.4; version=16.12.5; version=16.12.6; version=16.12.7; version=16.12.8; version=16.2.1; version=16.2.2; version=16.3.1; version=16.3.10; version=16.3.11; version=16.3.1a; version=16.3.2; version=16.3.3; version=16.3.4; version=16.3.5; version=16.3.6; version=16.3.7; version=16.3.8; version=16.3.9; version=16.4.1; version=16.4.2; version=16.4.3; version=16.5.1; version=16.5.1b; version=16.5.2; version=16.5.3; version=16.6.1; version=16.6.10; version=16.6.2; version=16.6.3; version=16.6.4; version=16.6.5; version=16.6.6; version=16.6.7; version=16.6.8; version=16.6.9; version=16.7.1; version=16.7.2; version=16.7.3; version=16.8.1; version=16.8.1s; version=16.8.2; version=16.8.3; version=16.9.1; version=16.9.1s; version=16.9.2; version=16.9.3; version=16.9.4; version=16.9.5; version=16.9.6; version=16.9.7; version=16.9.8; version=17.10.1; version=17.10.1a; version=17.1.1; version=17.11.1; version=17.11.1a; version=17.1.1s; version=17.1.1t; version=17.1.3; version=17.2.1; version=17.2.1r; version=17.2.1v; version=17.2.2; version=17.2.3; version=17.3.1; version=17.3.1a; version=17.3.2; version=17.3.3; version=17.3.4; version=17.3.4a; version=17.3.5; version=17.3.6; version=17.3.7; version=17.4.1; version=17.4.1a; version=17.4.1b; version=17.4.2; version=17.5.1; version=17.5.1a; version=17.5.1b; version=17.5.1c; version=17.6.1; version=17.6.1a; version=17.6.2; version=17.6.3; version=17.6.3a; version=17.6.4; version=17.6.5; version=17.6.5a; version=17.7.1; version=17.7.1a; version=17.7.2; version=17.8.1; version=17.8.1a; version=17.9.1; version=17.9.1a; version=17.9.2; version=17.9.2a; version=17.9.3; version=17.9.3a; version=3.10.0S; version=3.10.10S; version=3.10.1S; version=3.10.1xbS; version=3.10.2S; version=3.10.3S; version=3.10.4S; version=3.10.5S; version=3.10.6S; version=3.10.7S; version=3.10.8aS; version=3.10.8S; version=3.10.9S; version=3.11.0S; version=3.11.1S; version=3.11.2S; version=3.11.3S; version=3.11.4S; version=3.12.0S; version=3.12.1S; version=3.12.2S; version=3.12.3S; version=3.12.4S; version=3.13.0S; version=3.13.10S; version=3.13.1S; version=3.13.2aS; version=3.13.2S; version=3.13.3S; version=3.13.4S; version=3.13.5aS; version=3.13.5S; version=3.13.6aS; version=3.13.6S; version=3.13.7S; version=3.13.8S; version=3.13.9S; version=3.14.0S; version=3.14.1S; version=3.14.2S; version=3.14.3S; version=3.14.4S; version=3.15.0S; version=3.15.1S; version=3.15.2S; version=3.15.3S; version=3.15.4S; version=3.16.0S; version=3.16.10S; version=3.16.1aS; version=3.16.2bS; version=3.16.2S; version=3.16.3S; version=3.16.4aS; version=3.16.4bS; version=3.16.5S; version=3.16.6bS; version=3.16.6S; version=3.16.7aS; version=3.16.7bS; version=3.16.7S; version=3.16.8S; version=3.16.9S; version=3.17.0S; version=3.17.1aS; version=3.17.1S; version=3.17.2S; version=3.17.3S; version=3.17.4S; version=3.7.1S; version=3.7.2S; version=3.7.2tS; version=3.7.3S; version=3.7.4S; version=3.7.5S; version=3.7.6S; version=3.7.7S; version=3.8.0S; version=3.8.1S; version=3.8.2S; version=3.9.0S; version=3.9.1S; version=3.9.2S

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 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-823Use of Out-of-range Pointer Offset
CAPEC-129Pointer Manipulation
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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