CVE-2025-20241

Routing-process restart via insufficient IS-IS packet validation

Published Aug 27, 2025 · Updated Aug 27, 2025

Denial of service in Cisco NX-OS Software on affected Nexus switches allows attackers to restart IS-IS with a crafted packet. The IS-IS parser insufficiently validates an ingress IS-IS packet before processing it, and the resulting process restart can reload the device. Exploitation requires an IS-IS peer in the UP state with Layer 2 adjacency; enabled IS-IS authentication also requires a valid key.

CVSS severity7.4
High
EPSS probability0.27%
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 NX-OS Software on affected Nexus switches allows attackers to restart IS-IS with a crafted packet. The IS-IS parser insufficiently validates an ingress IS-IS packet before processing it, and the resulting process restart can reload the device. Exploitation requires an IS-IS peer in the UP state with Layer 2 adjacency; enabled IS-IS authentication also requires a valid key.

The record

CVE
CVE-2025-20241
Published
Aug 27, 2025
Updated
Aug 27, 2025
Vendor
ClamAV
Product
Cisco NX-OS Software
Classifications
CWE-733, T1498
Attack vector
adjacent
Privileges
unauthenticated

Timeline

How it unfolded

  1. Aug 27, 2025CVE publishedPublication date reported by the CVE source.
  2. Aug 27, 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=10.1(1)
  2. Affected versionversion=10.1(2)
  3. Affected versionversion=10.1(2t)
  4. Affected versionversion=10.2(1)
  5. Affected versionversion=10.2(1q)
  6. Affected versionversion=10.2(2)
  7. Affected versionversion=10.2(2a)
  8. Affected versionversion=10.2(3)
  9. Affected versionversion=10.2(3t)
  10. Affected versionversion=10.2(3v)
  11. Affected versionversion=10.2(4)
  12. Affected versionversion=10.2(5)
  13. Affected versionversion=10.2(6)
  14. Affected versionversion=10.2(7)
  15. Affected versionversion=10.2(8)
  16. Affected versionversion=10.3(1)
  17. Affected versionversion=10.3(2)
  18. Affected versionversion=10.3(3)
  19. Affected versionversion=10.3(3o)
  20. Affected versionversion=10.3(3p)
  21. Affected versionversion=10.3(3q)
  22. Affected versionversion=10.3(3r)
  23. Affected versionversion=10.3(3w)
  24. Affected versionversion=10.3(3x)
  25. Affected versionversion=10.3(4)
  26. Affected versionversion=10.3(4a)
  27. Affected versionversion=10.3(4g)
  28. Affected versionversion=10.3(4h)
  29. Affected versionversion=10.3(5)
  30. Affected versionversion=10.3(6)
  31. Affected versionversion=10.3(99w)
  32. Affected versionversion=10.3(99x)
  33. Affected versionversion=10.4(1)
  34. Affected versionversion=10.4(2)
  35. Affected versionversion=10.4(3)
  36. Affected versionversion=10.4(4)
  37. Affected versionversion=10.4(4g)
  38. Affected versionversion=10.5(1)
  39. Affected versionversion=10.5(2)
  40. Affected versionversion=6.0(2)A8(1)
  41. Affected versionversion=6.0(2)A8(10)
  42. Affected versionversion=6.0(2)A8(10a)
  43. Affected versionversion=6.0(2)A8(11)
  44. Affected versionversion=6.0(2)A8(11a)
  45. Affected versionversion=6.0(2)A8(11b)
  46. Affected versionversion=6.0(2)A8(2)
  47. Affected versionversion=6.0(2)A8(3)
  48. Affected versionversion=6.0(2)A8(4)
  49. Affected versionversion=6.0(2)A8(4a)
  50. Affected versionversion=6.0(2)A8(5)
  51. Affected versionversion=6.0(2)A8(6)
  52. Affected versionversion=6.0(2)A8(7)
  53. Affected versionversion=6.0(2)A8(7a)
  54. Affected versionversion=6.0(2)A8(7b)
  55. Affected versionversion=6.0(2)A8(8)
  56. Affected versionversion=6.0(2)A8(9)
  57. Affected versionversion=7.0(3)F3(1)
  58. Affected versionversion=7.0(3)F3(2)
  59. Affected versionversion=7.0(3)F3(3)
  60. Affected versionversion=7.0(3)F3(3a)
  61. Affected versionversion=7.0(3)F3(3c)
  62. Affected versionversion=7.0(3)F3(4)
  63. Affected versionversion=7.0(3)F3(5)
  64. Affected versionversion=7.0(3)I4(1)
  65. Affected versionversion=7.0(3)I4(1t)
  66. Affected versionversion=7.0(3)I4(2)
  67. Affected versionversion=7.0(3)I4(3)
  68. Affected versionversion=7.0(3)I4(4)
  69. Affected versionversion=7.0(3)I4(5)
  70. Affected versionversion=7.0(3)I4(6)
  71. Affected versionversion=7.0(3)I4(6t)
  72. Affected versionversion=7.0(3)I4(7)
  73. Affected versionversion=7.0(3)I4(8)
  74. Affected versionversion=7.0(3)I4(8a)
  75. Affected versionversion=7.0(3)I4(8b)
  76. Affected versionversion=7.0(3)I4(8z)
  77. Affected versionversion=7.0(3)I4(9)
  78. Affected versionversion=7.0(3)I5(1)
  79. Affected versionversion=7.0(3)I5(2)
  80. Affected versionversion=7.0(3)I5(3)
  81. Affected versionversion=7.0(3)I5(3a)
  82. Affected versionversion=7.0(3)I5(3b)
  83. Affected versionversion=7.0(3)I6(1)
  84. Affected versionversion=7.0(3)I6(2)
  85. Affected versionversion=7.0(3)I7(1)
  86. Affected versionversion=7.0(3)I7(10)
  87. Affected versionversion=7.0(3)I7(2)
  88. Affected versionversion=7.0(3)I7(3)
  89. Affected versionversion=7.0(3)I7(3z)
  90. Affected versionversion=7.0(3)I7(4)
  91. Affected versionversion=7.0(3)I7(5)
  92. Affected versionversion=7.0(3)I7(5a)
  93. Affected versionversion=7.0(3)I7(6)
  94. Affected versionversion=7.0(3)I7(6z)
  95. Affected versionversion=7.0(3)I7(7)
  96. Affected versionversion=7.0(3)I7(8)
  97. Affected versionversion=7.0(3)I7(9)
  98. Affected versionversion=7.0(3)I7(9w)
  99. Affected versionversion=7.0(3)IA7(1)
  100. Affected versionversion=7.0(3)IA7(2)
  101. Affected versionversion=7.0(3)IC4(4)
  102. Affected versionversion=7.0(3)IM7(2)
  103. Affected versionversion=9.2(1)
  104. Affected versionversion=9.2(2)
  105. Affected versionversion=9.2(2t)
  106. Affected versionversion=9.2(2v)
  107. Affected versionversion=9.2(3)
  108. Affected versionversion=9.2(3y)
  109. Affected versionversion=9.2(4)
  110. Affected versionversion=9.3(1)
  111. Affected versionversion=9.3(10)
  112. Affected versionversion=9.3(11)
  113. Affected versionversion=9.3(12)
  114. Affected versionversion=9.3(13)
  115. Affected versionversion=9.3(14)
  116. Affected versionversion=9.3(1z)
  117. Affected versionversion=9.3(2)
  118. Affected versionversion=9.3(3)
  119. Affected versionversion=9.3(4)
  120. Affected versionversion=9.3(5)
  121. Affected versionversion=9.3(5w)
  122. Affected versionversion=9.3(6)
  123. Affected versionversion=9.3(7)
  124. Affected versionversion=9.3(7a)
  125. Affected versionversion=9.3(7k)
  126. Affected versionversion=9.3(8)
  127. Affected versionversion=9.3(9)

What conditions does exploitation require?

Attack vectoradjacent
Required privilegesunauthenticated

What is affected?

ClamAV · Cisco NX-OS Softwareversion=10.1(1); version=10.1(2); version=10.1(2t); version=10.2(1); version=10.2(1q); version=10.2(2); version=10.2(2a); version=10.2(3); version=10.2(3t); version=10.2(3v); version=10.2(4); version=10.2(5); version=10.2(6); version=10.2(7); version=10.2(8); version=10.3(1); version=10.3(2); version=10.3(3); version=10.3(3o); version=10.3(3p); version=10.3(3q); version=10.3(3r); version=10.3(3w); version=10.3(3x); version=10.3(4); version=10.3(4a); version=10.3(4g); version=10.3(4h); version=10.3(5); version=10.3(6); version=10.3(99w); version=10.3(99x); version=10.4(1); version=10.4(2); version=10.4(3); version=10.4(4); version=10.4(4g); version=10.5(1); version=10.5(2); version=6.0(2)A8(1); version=6.0(2)A8(10); version=6.0(2)A8(10a); version=6.0(2)A8(11); version=6.0(2)A8(11a); version=6.0(2)A8(11b); version=6.0(2)A8(2); version=6.0(2)A8(3); version=6.0(2)A8(4); version=6.0(2)A8(4a); version=6.0(2)A8(5); version=6.0(2)A8(6); version=6.0(2)A8(7); version=6.0(2)A8(7a); version=6.0(2)A8(7b); version=6.0(2)A8(8); version=6.0(2)A8(9); version=7.0(3)F3(1); version=7.0(3)F3(2); version=7.0(3)F3(3); version=7.0(3)F3(3a); version=7.0(3)F3(3c); version=7.0(3)F3(4); version=7.0(3)F3(5); version=7.0(3)I4(1); version=7.0(3)I4(1t); version=7.0(3)I4(2); version=7.0(3)I4(3); version=7.0(3)I4(4); version=7.0(3)I4(5); version=7.0(3)I4(6); version=7.0(3)I4(6t); version=7.0(3)I4(7); version=7.0(3)I4(8); version=7.0(3)I4(8a); version=7.0(3)I4(8b); version=7.0(3)I4(8z); version=7.0(3)I4(9); version=7.0(3)I5(1); version=7.0(3)I5(2); version=7.0(3)I5(3); version=7.0(3)I5(3a); version=7.0(3)I5(3b); version=7.0(3)I6(1); version=7.0(3)I6(2); version=7.0(3)I7(1); version=7.0(3)I7(10); version=7.0(3)I7(2); version=7.0(3)I7(3); version=7.0(3)I7(3z); version=7.0(3)I7(4); version=7.0(3)I7(5); version=7.0(3)I7(5a); version=7.0(3)I7(6); version=7.0(3)I7(6z); version=7.0(3)I7(7); version=7.0(3)I7(8); version=7.0(3)I7(9); version=7.0(3)I7(9w); version=7.0(3)IA7(1); version=7.0(3)IA7(2); version=7.0(3)IC4(4); version=7.0(3)IM7(2); version=9.2(1); version=9.2(2); version=9.2(2t); version=9.2(2v); version=9.2(3); version=9.2(3y); version=9.2(4); version=9.3(1); version=9.3(10); version=9.3(11); version=9.3(12); version=9.3(13); version=9.3(14); version=9.3(1z); version=9.3(2); version=9.3(3); version=9.3(4); version=9.3(5); version=9.3(5w); version=9.3(6); version=9.3(7); version=9.3(7a); version=9.3(7k); version=9.3(8); version=9.3(9)

Published CVSS scores

7.4Cisco Systems, Inc.CVSS:3.1/AV:A/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)
Vectoradjacent
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-733Compiler Optimization Removal or Modification of Security-critical Code
T1498Network Denial of Service

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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