CVE-2026-20293 PUBLISHED

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

Assigner: cisco
Reserved: 08.10.2025 Published: 08.09.2026 Updated: 08.09.2026

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.

Metrics

CVSS 3.1

CVSS Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N
CVSS Score: 7.1

Attack Vector	Local	Scope	Unchanged
Attack Complexity	Low	Confidentiality Impact	High
Privileges Required	Low	Integrity Impact	High
User Interaction	None	Availability Impact	None

CVSS 3.1

Product Status

Vendor	Cisco
Product	Cisco Enterprise NFV Infrastructure Software
Versions	Default: unknown Version 4.1.1 is affected Version 3.9.1 is affected Version 3.5.2 is affected Version 3.12.2 is affected Version 3.6.2 is affected Version 3.9.2 is affected Version 3.11.3 is affected Version 3.11.1 is affected Version 3.5.1 is affected Version 3.3.1 is affected Version 3.10.2 is affected Version 3.12.1b is affected Version 3.4.1 is affected Version 3.12.1a is affected Version 3.6.3 is affected Version 3.8.1 is affected Version 3.11.2 is affected Version 3.12.1 is affected Version 3.12.3 is affected Version 3.10.1 is affected Version 3.6.1 is affected Version 3.10.3 is affected Version 3.7.1 is affected Version 4.1.2 is affected Version 4.2.1 is affected Version 4.2.2 is affected Version 4.4.1 is affected Version 4.4.2 is affected Version 4.5.1 is affected Version 4.4.3 is affected Version 4.6.1 is affected Version 4.7.1 is affected Version 4.6.2-FC2 is affected Version 4.6.2 is affected Version 4.8.1 is affected Version 4.8.2 is affected Version 4.9.1 is affected Version 4.6.3 is affected Version 4.9.2 is affected Version 4.10.1 is affected Version 4.9.3 is affected Version 4.11.1 is affected Version 4.9.4 is affected Version 4.12.1 is affected Version 4.6.4 is affected Version 4.12.2 is affected Version 4.13.1 is affected Version 4.9.5 is affected Version 4.12.3 is affected Version 4.14.1 is affected Version 4.6.3-FC4 is affected Version 4.9.4-FC3 is affected Version 4.12.4 is affected Version 4.15.1 is affected Version 4.9.6 is affected Version 4.15.2 is affected Version 4.12.5 is affected Version 4.15.3 is affected Version 4.15.4 is affected Version 4.12.6 is affected Version 4.15.5 is affected Version 4.12.7 is affected Version 4.12.8 is affected Version 4.15.6 is affected Version 4.9.10 is affected

Vendor	Cisco
Product	Cisco Unified Computing System (Managed)
Versions	Default: unknown Version 4.0(1a) is affected Version 4.1(1a) is affected Version 4.1(1b) is affected Version 4.0(4h) is affected Version 4.1(1c) is affected Version 4.0(4e) is affected Version 4.0(4g) is affected Version 4.0(2e) is affected Version 4.0(4a) is affected Version 4.0(2d) is affected Version 4.0(1b) is affected Version 4.0(4f) is affected Version 4.0(4c) is affected Version 4.0(1c) is affected Version 4.0(4b) is affected Version 4.0(2b) is affected Version 4.0(4d) is affected Version 4.0(2a) is affected Version 4.0(1d) is affected Version 4.0(4i) is affected Version 4.1(1d) is affected Version 4.1(2a) is affected Version 4.1(1e) is affected Version 4.1(2b) is affected Version 4.0(4k) is affected Version 4.1(3a) is affected Version 4.1(3b) is affected Version 4.1(2c) is affected Version 4.0(4l) is affected Version 4.1(4a) is affected Version 4.1(3c) is affected Version 4.1(3d) is affected Version 4.2(1c) is affected Version 4.2(1d) is affected Version 4.0(4m) is affected Version 4.1(3e) is affected Version 4.2(1f) is affected Version 4.1(3f) is affected Version 4.2(1i) is affected Version 4.2(1k) is affected Version 4.0(4n) is affected Version 4.1(3h) is affected Version 4.2(1l) is affected Version 4.2(1m) is affected Version 4.1(3i) is affected Version 4.2(2a) is affected Version 4.2(1n) is affected Version 4.1(3j) is affected Version 4.2(2c) is affected Version 4.2(2d) is affected Version 4.2(3b) is affected Version 4.1(3k) is affected Version 4.0(4o) is affected Version 4.2(2e) is affected Version 4.2(3d) is affected Version 4.2(3e) is affected Version 4.2(3g) is affected Version 4.1(3l) is affected Version 4.3(2b) is affected Version 4.2(3h) is affected Version 4.2(3i) is affected Version 4.3(2c) is affected Version 4.1(3m) is affected Version 4.3(2e) is affected Version 4.3(3a) is affected Version 4.2(3j) is affected Version 4.3(3c) is affected Version 4.3(4a) is affected Version 4.2(3k) is affected Version 4.3(4b) is affected Version 4.3(4c) is affected Version 4.2(3l) is affected Version 4.3(4d) is affected Version 4.2(3m) is affected Version 4.3(2f) is affected Version 4.3(5a) is affected Version 4.3(4e) is affected Version 4.1(3n) is affected Version 4.3(4f) is affected Version 4.2(3n) is affected Version 4.3(5c) is affected Version 4.2(3o) is affected Version 4.3(5d) is affected Version 4.3(6a) is affected Version 4.3(6b) is affected Version 4.3(5e) is affected Version 4.3(6c) is affected Version 6.0(1b) is affected Version 4.2(3p) is affected Version 6.0(1c) is affected Version 4.3(6d) is affected Version 6.0(1d) is affected Version 6.0(1e) is affected Version 4.3(6e) is affected Version 6.0(1f) is affected Version 4.3(6f) is affected Version 6.0(2b) is affected Version 6.0(1h) is affected Version 4.2(3r) is affected Version 6.0(2c) is affected Version 4.3(6g) is affected

Vendor	Cisco
Product	Cisco Unified Computing System (Standalone)
Versions	Default: unknown Version 4.0(2g) is affected Version 3.1(2i) is affected Version 3.1(1d) is affected Version 4.0(4i) is affected Version 4.1(1c) is affected Version 4.0(2c) is affected Version 4.0(1e) is affected Version 4.0(2h) is affected Version 4.0(4h) is affected Version 4.0(1h) is affected Version 4.0(2l) is affected Version 3.1(3g) is affected Version 4.0(1.240) is affected Version 4.0(2f) is affected Version 4.0(1g) is affected Version 4.0(2i) is affected Version 3.1(3i) is affected Version 4.0(4d) is affected Version 4.1(1d) is affected Version 3.1(3c) is affected Version 4.0(4k) is affected Version 3.1(2d) is affected Version 3.1(3a) is affected Version 3.1(3j) is affected Version 4.0(2d) is affected Version 4.1(1f) is affected Version 4.0(4j) is affected Version 4.0(2m) is affected Version 4.0(2k) is affected Version 4.0(1c) is affected Version 4.0(4f) is affected Version 4.0(4c) is affected Version 3.1(3d) is affected Version 3.1(2g) is affected Version 3.1(2c) is affected Version 4.0(1d) is affected Version 3.1(2e) is affected Version 4.0(1a) is affected Version 4.0(1b) is affected Version 3.1(3b) is affected Version 4.0(4b) is affected Version 3.1(2b) is affected Version 4.0(4e) is affected Version 3.1(3h) is affected Version 4.0(4l) is affected Version 4.1(1g) is affected Version 4.1(2a) is affected Version 4.0(2n) is affected Version 4.1(1h) is affected Version 3.1(3k) is affected Version 4.1(2b) is affected Version 4.0(2o) is affected Version 4.0(4m) is affected Version 4.1(2d) is affected Version 4.1(3b) is affected Version 4.0(2p) is affected Version 4.1(2e) is affected Version 4.1(2f) is affected Version 4.0(4n) is affected Version 4.0(2q) is affected Version 4.1(3c) is affected Version 4.0(2r) is affected Version 4.1(3d) is affected Version 4.1(2g) is affected Version 4.1(2h) is affected Version 4.1(3g) is affected Version 4.1(3f) is affected Version 4.1(2j) is affected Version 4.1(2k) is affected Version 4.1(3h) is affected Version 4.2(2a) is affected Version 4.1(3i) is affected Version 4.2(2f) is affected Version 4.2(2g) is affected Version 4.2(3b) is affected Version 4.1(3l) is affected Version 4.2(3d) is affected Version 4.3(1.230097) is affected Version 4.2(1e) is affected Version 4.2(1b) is affected Version 4.2(1j) is affected Version 4.2(1i) is affected Version 4.2(1f) is affected Version 4.2(1a) is affected Version 4.2(1c) is affected Version 4.2(1g) is affected Version 4.3(1.230124) is affected Version 4.1(2l) is affected Version 4.2(3e) is affected Version 4.3(1.230138) is affected Version 4.2(3g) is affected Version 4.3(2.230207) is affected Version 4.2(3h) is affected Version 4.2(3i) is affected Version 4.3(2.230270) is affected Version 4.1(3m) is affected Version 4.1(2m) is affected Version 4.3(2.240002) is affected Version 4.3(3.240022) is affected Version 4.2(3j) is affected Version 4.1(3n) is affected Version 4.3(2.240009) is affected Version 4.3(3.240041) is affected Version 4.2(3k) is affected Version 4.3(3.240043) is affected Version 4.3(4.240142) is affected Version 4.3(2.240037) is affected Version 4.3(2.240053) is affected Version 4.3(4.240152) is affected Version 4.2(3l) is affected Version 4.3(2.240077) is affected Version 4.3(4.242028) is affected Version 4.3(4.241063) is affected Version 4.3(4.242038) is affected Version 4.2(3m) is affected Version 4.3(2.240090) is affected Version 4.3(5.240021) is affected Version 4.3(2.240107) is affected Version 4.3(4.242066) is affected Version 4.2(3n) is affected Version 4.3(5.250001) is affected Version 4.2(3o) is affected Version 4.3(2.250016) is affected Version 4.3(2.250021) is affected Version 4.3(5.250030) is affected Version 4.3(2.250022) is affected Version 4.3(6.250039) is affected Version 4.3(6.250040) is affected Version 4.3(5.250033) is affected Version 4.3(6.250044) is affected Version 4.3(6.250053) is affected Version 4.3(2.250037) is affected Version 4.3(2.250045) is affected Version 4.3(4.252001) is affected Version 4.3(4.252002) is affected Version 6.0(1.250127) is affected Version 4.2(3p) is affected Version 6.0(1.250131) is affected Version 4.3(6.250101) is affected Version 6.0(1.250174) is affected Version 4.3(6.250117) is affected Version 4.3(5.250043) is affected Version 4.3(5.250045) is affected Version 4.3(6.250060) is affected Version 6.0(1.250130) is affected Version 4.3(4.241014) is affected Version 6.0(1.251030) is affected Version 4.3(2.250063) is affected Version 6.0(1.250192) is affected Version 4.3(6.260003) is affected Version 6.0(1.250194) is affected Version 6.0(1.260001) is affected Version 4.3(6.260017) is affected Version 4.3(2.260007) is affected Version 6.0(2.260044) is affected Version 6.0(2.260042) is affected Version 4.0(1.260003) is affected Version 2.0(2.260062) is affected Version 2.0(1.250127) is affected Version 2.0(1.250096) is affected Version 4.0(1.260004) is affected Version 6.0(2.260026) is affected Version 6.0(1.251006) is affected Version 1.2(0.250011) is affected Version 1.1(0.250016) is affected Version 1.0(0.240001) is affected Version 1.0(0.250003) is affected Version 1.2(0.250013) is affected Version 1.1(0.250026) is affected Version 1.0(1.250002) is affected Version 1.1(0.250022) is affected Version 1.1(0.250025) is affected Version 1.0(1.250032) is affected Version 6.0(2.260034) is affected Version 6.0(2.260069) is affected Version 4.3(6.260033) is affected Version 2.0(2.260101) is affected Version 4.2(3q) is affected Version 4.2(3r) is affected Version 1.2(0.260005) is affected

Vendor	Cisco
Product	Cisco Unified Computing System E-Series Software (UCSE)
Versions	Default: unknown Version 4.11.1 is affected Version 4.12.1 is affected Version 4.12.2 is affected Version 4.15.2 is affected Version 4.15.3 is affected Version 4.15.4 is affected

Exploits

The Cisco PSIRT is aware that proof-of-concept exploit code is available for the vulnerability described in this advisory.

The Cisco PSIRT is not aware of any malicious use of the vulnerability that is described in this advisory.

References

cisco-sa-ucs-uefi-sb-bypass-eb6xC5GW

Problem Types

Exposed Dangerous Method or Function cwe