CVE-2026-20293

HIGH 7.1

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

CVSS Score

7.1

EPSS Score

0.0%

EPSS Percentile

0th

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.

CWE	CWE-749
Vendor	cisco
Product	cisco enterprise nfv infrastructure software
Ecosystems	Networking
Industries	NetworkingTelecommunications
Published	Sep 8, 2026
Last Updated	Sep 11, 2026

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CVSS v3 Breakdown

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N

Attack Vector

Local

Attack Complexity

Low

Privileges Required

Low

User Interaction

None

Scope

Unchanged

Confidentiality

High

Integrity

High

Availability

None

Affected Versions

Cisco / Cisco Enterprise NFV Infrastructure Software

4.1.1 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

Cisco / Cisco Unified Computing System (Managed)

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)

Cisco / Cisco Unified Computing System (Standalone)

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)

Cisco / Cisco Unified Computing System E-Series Software (UCSE)

4.11.1 4.12.1 4.12.2 4.15.2 4.15.3 4.15.4

References

NVD ↗ CVE.org ↗ EPSS Data ↗

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