CVE-2026-20293

Secure Boot bypass via UEFI memory writes

Published Sep 8, 2026 · Updated Sep 8, 2026

Secure Boot bypass in Cisco UCS servers and UCS-based appliances allows local users to execute unauthorized software through the UEFI Shell. The shell leaves memory-write commands available while Secure Boot is enabled, allowing UEFI memory variables used by validation to be overwritten. Exploitation requires a user or administrator account and console access, or unauthenticated physical access; successful attacks can alter the preboot trust boundary without interrupting service.

CVSS severity7.1
High
EPSS probability0.13%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
Coverage for this vulnerability

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Summary

What happened

Secure Boot bypass in Cisco UCS servers and UCS-based appliances allows local users to execute unauthorized software through the UEFI Shell. The shell leaves memory-write commands available while Secure Boot is enabled, allowing UEFI memory variables used by validation to be overwritten. Exploitation requires a user or administrator account and console access, or unauthenticated physical access; successful attacks can alter the preboot trust boundary without interrupting service.

The record

CVE
CVE-2026-20293
Published
Sep 8, 2026
Updated
Sep 8, 2026
Vendor
ClamAV
Product
Cisco Unified Computing System (Managed)
Classifications
CWE-749, T1542.001
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Sep 8, 2026CVE publishedPublication date reported by the CVE source.
  2. Sep 8, 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=4.0(1a)
  2. Affected versionversion=4.0(1b)
  3. Affected versionversion=4.0(1c)
  4. Affected versionversion=4.0(1d)
  5. Affected versionversion=4.0(2a)
  6. Affected versionversion=4.0(2b)
  7. Affected versionversion=4.0(2d)
  8. Affected versionversion=4.0(2e)
  9. Affected versionversion=4.0(4a)
  10. Affected versionversion=4.0(4b)
  11. Affected versionversion=4.0(4c)
  12. Affected versionversion=4.0(4d)
  13. Affected versionversion=4.0(4e)
  14. Affected versionversion=4.0(4f)
  15. Affected versionversion=4.0(4g)
  16. Affected versionversion=4.0(4h)
  17. Affected versionversion=4.0(4i)
  18. Affected versionversion=4.0(4k)
  19. Affected versionversion=4.0(4l)
  20. Affected versionversion=4.0(4m)
  21. Affected versionversion=4.0(4n)
  22. Affected versionversion=4.0(4o)
  23. Affected versionversion=4.1(1a)
  24. Affected versionversion=4.1(1b)
  25. Affected versionversion=4.1(1c)
  26. Affected versionversion=4.1(1d)
  27. Affected versionversion=4.1(1e)
  28. Affected versionversion=4.1(2a)
  29. Affected versionversion=4.1(2b)
  30. Affected versionversion=4.1(2c)
  31. Affected versionversion=4.1(3a)
  32. Affected versionversion=4.1(3b)
  33. Affected versionversion=4.1(3c)
  34. Affected versionversion=4.1(3d)
  35. Affected versionversion=4.1(3e)
  36. Affected versionversion=4.1(3f)
  37. Affected versionversion=4.1(3h)
  38. Affected versionversion=4.1(3i)
  39. Affected versionversion=4.1(3j)
  40. Affected versionversion=4.1(3k)
  41. Affected versionversion=4.1(3l)
  42. Affected versionversion=4.1(3m)
  43. Affected versionversion=4.1(3n)
  44. Affected versionversion=4.1(4a)
  45. Affected versionversion=4.2(1c)
  46. Affected versionversion=4.2(1d)
  47. Affected versionversion=4.2(1f)
  48. Affected versionversion=4.2(1i)
  49. Affected versionversion=4.2(1k)
  50. Affected versionversion=4.2(1l)
  51. Affected versionversion=4.2(1m)
  52. Affected versionversion=4.2(1n)
  53. Affected versionversion=4.2(2a)
  54. Affected versionversion=4.2(2c)
  55. Affected versionversion=4.2(2d)
  56. Affected versionversion=4.2(2e)
  57. Affected versionversion=4.2(3b)
  58. Affected versionversion=4.2(3d)
  59. Affected versionversion=4.2(3e)
  60. Affected versionversion=4.2(3g)
  61. Affected versionversion=4.2(3h)
  62. Affected versionversion=4.2(3i)
  63. Affected versionversion=4.2(3j)
  64. Affected versionversion=4.2(3k)
  65. Affected versionversion=4.2(3l)
  66. Affected versionversion=4.2(3m)
  67. Affected versionversion=4.2(3n)
  68. Affected versionversion=4.2(3o)
  69. Affected versionversion=4.2(3p)
  70. Affected versionversion=4.2(3r)
  71. Affected versionversion=4.3(2b)
  72. Affected versionversion=4.3(2c)
  73. Affected versionversion=4.3(2e)
  74. Affected versionversion=4.3(2f)
  75. Affected versionversion=4.3(3a)
  76. Affected versionversion=4.3(3c)
  77. Affected versionversion=4.3(4a)
  78. Affected versionversion=4.3(4b)
  79. Affected versionversion=4.3(4c)
  80. Affected versionversion=4.3(4d)
  81. Affected versionversion=4.3(4e)
  82. Affected versionversion=4.3(4f)
  83. Affected versionversion=4.3(5a)
  84. Affected versionversion=4.3(5c)
  85. Affected versionversion=4.3(5d)
  86. Affected versionversion=4.3(5e)
  87. Affected versionversion=4.3(6a)
  88. Affected versionversion=4.3(6b)
  89. Affected versionversion=4.3(6c)
  90. Affected versionversion=4.3(6d)
  91. Affected versionversion=4.3(6e)
  92. Affected versionversion=4.3(6f)
  93. Affected versionversion=4.3(6g)
  94. Affected versionversion=6.0(1b)
  95. Affected versionversion=6.0(1c)
  96. Affected versionversion=6.0(1d)
  97. Affected versionversion=6.0(1e)
  98. Affected versionversion=6.0(1f)
  99. Affected versionversion=6.0(1h)
  100. Affected versionversion=6.0(2b)
  101. Affected versionversion=6.0(2c)

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

ClamAV · Cisco Unified Computing System (Managed)version=4.0(1a); version=4.0(1b); version=4.0(1c); version=4.0(1d); version=4.0(2a); version=4.0(2b); version=4.0(2d); version=4.0(2e); version=4.0(4a); version=4.0(4b); version=4.0(4c); version=4.0(4d); version=4.0(4e); version=4.0(4f); version=4.0(4g); version=4.0(4h); version=4.0(4i); version=4.0(4k); version=4.0(4l); version=4.0(4m); version=4.0(4n); version=4.0(4o); version=4.1(1a); version=4.1(1b); version=4.1(1c); version=4.1(1d); version=4.1(1e); version=4.1(2a); version=4.1(2b); version=4.1(2c); version=4.1(3a); version=4.1(3b); version=4.1(3c); version=4.1(3d); version=4.1(3e); version=4.1(3f); version=4.1(3h); version=4.1(3i); version=4.1(3j); version=4.1(3k); version=4.1(3l); version=4.1(3m); version=4.1(3n); version=4.1(4a); version=4.2(1c); version=4.2(1d); version=4.2(1f); version=4.2(1i); version=4.2(1k); version=4.2(1l); version=4.2(1m); version=4.2(1n); version=4.2(2a); version=4.2(2c); version=4.2(2d); version=4.2(2e); version=4.2(3b); version=4.2(3d); version=4.2(3e); version=4.2(3g); version=4.2(3h); version=4.2(3i); version=4.2(3j); version=4.2(3k); version=4.2(3l); version=4.2(3m); version=4.2(3n); version=4.2(3o); version=4.2(3p); version=4.2(3r); version=4.3(2b); version=4.3(2c); version=4.3(2e); version=4.3(2f); version=4.3(3a); version=4.3(3c); version=4.3(4a); version=4.3(4b); version=4.3(4c); version=4.3(4d); version=4.3(4e); version=4.3(4f); version=4.3(5a); version=4.3(5c); version=4.3(5d); version=4.3(5e); version=4.3(6a); version=4.3(6b); version=4.3(6c); version=4.3(6d); version=4.3(6e); version=4.3(6f); version=4.3(6g); version=6.0(1b); version=6.0(1c); version=6.0(1d); version=6.0(1e); version=6.0(1f); version=6.0(1h); version=6.0(2b); version=6.0(2c)
ClamAV · Cisco Enterprise NFV Infrastructure Softwareversion=3.10.1; version=3.10.2; version=3.10.3; version=3.11.1; version=3.11.2; version=3.11.3; version=3.12.1; version=3.12.1a; version=3.12.1b; version=3.12.2; version=3.12.3; version=3.3.1; version=3.4.1; version=3.5.1; version=3.5.2; version=3.6.1; version=3.6.2; version=3.6.3; version=3.7.1; version=3.8.1; version=3.9.1; version=3.9.2; version=4.10.1; version=4.1.1; version=4.11.1; version=4.1.2; version=4.12.1; version=4.12.2; version=4.12.3; version=4.12.4; version=4.12.5; version=4.12.6; version=4.12.7; version=4.12.8; version=4.13.1; version=4.14.1; version=4.15.1; version=4.15.2; version=4.15.3; version=4.15.4; version=4.15.5; version=4.15.6; version=4.2.1; version=4.2.2; version=4.4.1; version=4.4.2; version=4.4.3; version=4.5.1; version=4.6.1; version=4.6.2; version=4.6.2-FC2; version=4.6.3; version=4.6.3-FC4; version=4.6.4; version=4.7.1; version=4.8.1; version=4.8.2; version=4.9.1; version=4.9.10; version=4.9.2; version=4.9.3; version=4.9.4; version=4.9.4-FC3; version=4.9.5; version=4.9.6
ClamAV · Cisco Unified Computing System (Standalone)version=1.0(0.240001); version=1.0(0.250003); version=1.0(1.250002); version=1.0(1.250032); version=1.1(0.250016); version=1.1(0.250022); version=1.1(0.250025); version=1.1(0.250026); version=1.2(0.250011); version=1.2(0.250013); version=1.2(0.260005); version=2.0(1.250096); version=2.0(1.250127); version=2.0(2.260062); version=2.0(2.260101); version=3.1(1d); version=3.1(2b); version=3.1(2c); version=3.1(2d); version=3.1(2e); version=3.1(2g); version=3.1(2i); version=3.1(3a); version=3.1(3b); version=3.1(3c); version=3.1(3d); version=3.1(3g); version=3.1(3h); version=3.1(3i); version=3.1(3j); version=3.1(3k); version=4.0(1.240); version=4.0(1.260003); version=4.0(1.260004); version=4.0(1a); version=4.0(1b); version=4.0(1c); version=4.0(1d); version=4.0(1e); version=4.0(1g); version=4.0(1h); version=4.0(2c); version=4.0(2d); version=4.0(2f); version=4.0(2g); version=4.0(2h); version=4.0(2i); version=4.0(2k); version=4.0(2l); version=4.0(2m); version=4.0(2n); version=4.0(2o); version=4.0(2p); version=4.0(2q); version=4.0(2r); version=4.0(4b); version=4.0(4c); version=4.0(4d); version=4.0(4e); version=4.0(4f); version=4.0(4h); version=4.0(4i); version=4.0(4j); version=4.0(4k); version=4.0(4l); version=4.0(4m); version=4.0(4n); version=4.1(1c); version=4.1(1d); version=4.1(1f); version=4.1(1g); version=4.1(1h); version=4.1(2a); version=4.1(2b); version=4.1(2d); version=4.1(2e); version=4.1(2f); version=4.1(2g); version=4.1(2h); version=4.1(2j); version=4.1(2k); version=4.1(2l); version=4.1(2m); version=4.1(3b); version=4.1(3c); version=4.1(3d); version=4.1(3f); version=4.1(3g); version=4.1(3h); version=4.1(3i); version=4.1(3l); version=4.1(3m); version=4.1(3n); version=4.2(1a); version=4.2(1b); version=4.2(1c); version=4.2(1e); version=4.2(1f); version=4.2(1g); version=4.2(1i); version=4.2(1j); version=4.2(2a); version=4.2(2f); version=4.2(2g); version=4.2(3b); version=4.2(3d); version=4.2(3e); version=4.2(3g); version=4.2(3h); version=4.2(3i); version=4.2(3j); version=4.2(3k); version=4.2(3l); version=4.2(3m); version=4.2(3n); version=4.2(3o); version=4.2(3p); version=4.2(3q); version=4.2(3r); version=4.3(1.230097); version=4.3(1.230124); version=4.3(1.230138); version=4.3(2.230207); version=4.3(2.230270); version=4.3(2.240002); version=4.3(2.240009); version=4.3(2.240037); version=4.3(2.240053); version=4.3(2.240077); version=4.3(2.240090); version=4.3(2.240107); version=4.3(2.250016); version=4.3(2.250021); version=4.3(2.250022); version=4.3(2.250037); version=4.3(2.250045); version=4.3(2.250063); version=4.3(2.260007); version=4.3(3.240022); version=4.3(3.240041); version=4.3(3.240043); version=4.3(4.240142); version=4.3(4.240152); version=4.3(4.241014); version=4.3(4.241063); version=4.3(4.242028); version=4.3(4.242038); version=4.3(4.242066); version=4.3(4.252001); version=4.3(4.252002); version=4.3(5.240021); version=4.3(5.250001); version=4.3(5.250030); version=4.3(5.250033); version=4.3(5.250043); version=4.3(5.250045); version=4.3(6.250039); version=4.3(6.250040); version=4.3(6.250044); version=4.3(6.250053); version=4.3(6.250060); version=4.3(6.250101); version=4.3(6.250117); version=4.3(6.260003); version=4.3(6.260017); version=4.3(6.260033); version=6.0(1.250127); version=6.0(1.250130); version=6.0(1.250131); version=6.0(1.250174); version=6.0(1.250192); version=6.0(1.250194); version=6.0(1.251006); version=6.0(1.251030); version=6.0(1.260001); version=6.0(2.260026); version=6.0(2.260034); version=6.0(2.260042); version=6.0(2.260044); version=6.0(2.260069)
ClamAV · Cisco Unified Computing System E-Series Software (UCSE)version=4.11.1; version=4.12.1; version=4.12.2; version=4.15.2; version=4.15.3; version=4.15.4

Published CVSS scores

7.1CiscoCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N/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)
Vectorlocal
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-749Exposed Dangerous Method or Function
T1542.001Pre-OS Boot: System Firmware

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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