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7.1
CVE-2026-20293
Cisco · Cisco Enterprise NFV Infrastructure Software

Cisco UCS and UCS-Based Appliances UEFI Shell Secure Boot Bypass Vulnerability

Description

A vulnerability in the Unified Extensible Firmware Interface (UEFI) Shell implementation of Cisco UCS Servers and UCS-based appliances could allow an authenticated attacker with valid credentials for a user account with the role of user or admin or an unauthenticated attacker with physical access to an affected device to bypass UEFI Secure Boot validation checks and execute unauthorized software. This vulnerability is due to the availability of memory write commands in the UEFI Shell while UEFI Secure Boot is enabled on a device. An attacker could exploit this vulnerability by selecting the UEFI Shell boot option at boot time and using available shell commands to modify UEFI memory variables. A successful exploit could allow the attacker to manipulate the preboot environment, overwrite UEFI Secure Boot-related memory values, and execute unauthorized software on the affected device.

Affected Products

VendorProductVersions
CiscoCisco Enterprise NFV Infrastructure Software4.1.1, 3.9.1, 3.5.2, 3.12.2, 3.6.2, 3.9.2, 3.11.3, 3.11.1, 3.5.1, 3.3.1, 3.10.2, 3.12.1b, 3.4.1, 3.12.1a, 3.6.3, 3.8.1, 3.11.2, 3.12.1, 3.12.3, 3.10.1, 3.6.1, 3.10.3, 3.7.1, 4.1.2, 4.2.1, 4.2.2, 4.4.1, 4.4.2, 4.5.1, 4.4.3, 4.6.1, 4.7.1, 4.6.2-FC2, 4.6.2, 4.8.1, 4.8.2, 4.9.1, 4.6.3, 4.9.2, 4.10.1, 4.9.3, 4.11.1, 4.9.4, 4.12.1, 4.6.4, 4.12.2, 4.13.1, 4.9.5, 4.12.3, 4.14.1, 4.6.3-FC4, 4.9.4-FC3, 4.12.4, 4.15.1, 4.9.6, 4.15.2, 4.12.5, 4.15.3, 4.15.4, 4.12.6, 4.15.5, 4.12.7, 4.12.8, 4.15.6, 4.9.10, 4.0(1a), 4.1(1a), 4.1(1b), 4.0(4h), 4.1(1c), 4.0(4e), 4.0(4g), 4.0(2e), 4.0(4a), 4.0(2d), 4.0(1b), 4.0(4f), 4.0(4c), 4.0(1c), 4.0(4b), 4.0(2b), 4.0(4d), 4.0(2a), 4.0(1d), 4.0(4i), 4.1(1d), 4.1(2a), 4.1(1e), 4.1(2b), 4.0(4k), 4.1(3a), 4.1(3b), 4.1(2c), 4.0(4l), 4.1(4a), 4.1(3c), 4.1(3d), 4.2(1c), 4.2(1d), 4.0(4m), 4.1(3e), 4.2(1f), 4.1(3f), 4.2(1i), 4.2(1k), 4.0(4n), 4.1(3h), 4.2(1l), 4.2(1m), 4.1(3i), 4.2(2a), 4.2(1n), 4.1(3j), 4.2(2c), 4.2(2d), 4.2(3b), 4.1(3k), 4.0(4o), 4.2(2e), 4.2(3d), 4.2(3e), 4.2(3g), 4.1(3l), 4.3(2b), 4.2(3h), 4.2(3i), 4.3(2c), 4.1(3m), 4.3(2e), 4.3(3a), 4.2(3j), 4.3(3c), 4.3(4a), 4.2(3k), 4.3(4b), 4.3(4c), 4.2(3l), 4.3(4d), 4.2(3m), 4.3(2f), 4.3(5a), 4.3(4e), 4.1(3n), 4.3(4f), 4.2(3n), 4.3(5c), 4.2(3o), 4.3(5d), 4.3(6a), 4.3(6b), 4.3(5e), 4.3(6c), 6.0(1b), 4.2(3p), 6.0(1c), 4.3(6d), 6.0(1d), 6.0(1e), 4.3(6e), 6.0(1f), 4.3(6f), 6.0(2b), 6.0(1h), 4.2(3r), 6.0(2c), 4.3(6g), 4.0(2g), 3.1(2i), 3.1(1d), 4.0(4i), 4.1(1c), 4.0(2c), 4.0(1e), 4.0(2h), 4.0(4h), 4.0(1h), 4.0(2l), 3.1(3g), 4.0(1.240), 4.0(2f), 4.0(1g), 4.0(2i), 3.1(3i), 4.0(4d), 4.1(1d), 3.1(3c), 4.0(4k), 3.1(2d), 3.1(3a), 3.1(3j), 4.0(2d), 4.1(1f), 4.0(4j), 4.0(2m), 4.0(2k), 4.0(1c), 4.0(4f), 4.0(4c), 3.1(3d), 3.1(2g), 3.1(2c), 4.0(1d), 3.1(2e), 4.0(1a), 4.0(1b), 3.1(3b), 4.0(4b), 3.1(2b), 4.0(4e), 3.1(3h), 4.0(4l), 4.1(1g), 4.1(2a), 4.0(2n), 4.1(1h), 3.1(3k), 4.1(2b), 4.0(2o), 4.0(4m), 4.1(2d), 4.1(3b), 4.0(2p), 4.1(2e), 4.1(2f), 4.0(4n), 4.0(2q), 4.1(3c), 4.0(2r), 4.1(3d), 4.1(2g), 4.1(2h), 4.1(3g), 4.1(3f), 4.1(2j), 4.1(2k), 4.1(3h), 4.2(2a), 4.1(3i), 4.2(2f), 4.2(2g), 4.2(3b), 4.1(3l), 4.2(3d), 4.3(1.230097), 4.2(1e), 4.2(1b), 4.2(1j), 4.2(1i), 4.2(1f), 4.2(1a), 4.2(1c), 4.2(1g), 4.3(1.230124), 4.1(2l), 4.2(3e), 4.3(1.230138), 4.2(3g), 4.3(2.230207), 4.2(3h), 4.2(3i), 4.3(2.230270), 4.1(3m), 4.1(2m), 4.3(2.240002), 4.3(3.240022), 4.2(3j), 4.1(3n), 4.3(2.240009), 4.3(3.240041), 4.2(3k), 4.3(3.240043), 4.3(4.240142), 4.3(2.240037), 4.3(2.240053), 4.3(4.240152), 4.2(3l), 4.3(2.240077), 4.3(4.242028), 4.3(4.241063), 4.3(4.242038), 4.2(3m), 4.3(2.240090), 4.3(5.240021), 4.3(2.240107), 4.3(4.242066), 4.2(3n), 4.3(5.250001), 4.2(3o), 4.3(2.250016), 4.3(2.250021), 4.3(5.250030), 4.3(2.250022), 4.3(6.250039), 4.3(6.250040), 4.3(5.250033), 4.3(6.250044), 4.3(6.250053), 4.3(2.250037), 4.3(2.250045), 4.3(4.252001), 4.3(4.252002), 6.0(1.250127), 4.2(3p), 6.0(1.250131), 4.3(6.250101), 6.0(1.250174), 4.3(6.250117), 4.3(5.250043), 4.3(5.250045), 4.3(6.250060), 6.0(1.250130), 4.3(4.241014), 6.0(1.251030), 4.3(2.250063), 6.0(1.250192), 4.3(6.260003), 6.0(1.250194), 6.0(1.260001), 4.3(6.260017), 4.3(2.260007), 6.0(2.260044), 6.0(2.260042), 4.0(1.260003), 2.0(2.260062), 2.0(1.250127), 2.0(1.250096), 4.0(1.260004), 6.0(2.260026), 6.0(1.251006), 1.2(0.250011), 1.1(0.250016), 1.0(0.240001), 1.0(0.250003), 1.2(0.250013), 1.1(0.250026), 1.0(1.250002), 1.1(0.250022), 1.1(0.250025), 1.0(1.250032), 6.0(2.260034), 6.0(2.260069), 4.3(6.260033), 2.0(2.260101), 4.2(3q), 4.2(3r), 1.2(0.260005), 4.11.1, 4.12.1, 4.12.2, 4.15.2, 4.15.3, 4.15.4

Also Affects

Downstream vendors/products affected by this vulnerability

VendorProductSourceConfidence
ciscisco unified computing system (managed)mitre_affected90%
ciscisco unified computing system (standalone)mitre_affected90%
ciscisco unified computing system e-series software (ucse)mitre_affected90%
cisunified computing system (ucs)cert_advisory90%
insydeuefi firmwarecert_advisory90%

References

  • https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-ucs-uefi-sb-bypass-eb6xC5GW

Related News (5 articles)

Tier B
BSI Advisories18d ago
[NEU] [mittel] Insyde UEFI Firmware und Cisco UCS (UEFI Shell Secure Boot): Schwachstelle ermöglicht Umgehen von Sicherheitsvorkehrungen
→ No new info (linked only)
Tier B
CERT-FR19d ago
Vulnérabilité dans les produits Cisco (09 septembre 2026)
→ No new info (linked only)
Tier C
VulDB19d ago
CVE-2026-20293 | Cisco Unified Computing System UEFI Shell improper authorization
→ No new info (linked only)
Tier A
Cisco Security19d ago
Cisco UCS and UCS-Based Appliances UEFI Shell Secure Boot Bypass Vulnerability
→ No new info (linked only)
Tier B
CERT/CC Vuln Notes19d ago
VU#718077: UEFI Shell module embedded in SPI Flash can be used to bypass Secure Boot
→ No new info (linked only)

Discussion (0)

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CVSS 3.17.1 HIGH
VectorCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N
CISA KEV❌ No
Actively exploited❌ No
CWECWE-749
PublishedSep 8, 2026
Last enriched19d ago
Trending Score7
Source articles5
Independent5
Info Completeness8/14
Missing: epss, kev, exploit, patch, iocs, mitre_attack

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Verification

State: verified
Confidence: 0%

Vulnerability Timeline

CVE Published
Sep 8, 2026
Discovered by ZDM
Sep 8, 2026