CVE-2019-1736: Multiple Cisco UCS-Based Products UEFI Secure Boot Bypass Vulnerability

Severity: medium (CVSS 6.6 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.2% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2020-09-23 · updated 2026-06-17
Weakness: CWE-347

Description

A vulnerability in the firmware of the Cisco UCS C-Series Rack Servers could allow an authenticated, physical attacker to bypass Unified Extensible Firmware Interface (UEFI) Secure Boot validation checks and load a compromised software image on an affected device. The vulnerability is due to improper validation of the server firmware upgrade images. An attacker could exploit this vulnerability by installing a server firmware version that would allow the attacker to disable UEFI Secure Boot. A successful exploit could allow the attacker to bypass the signature validation checks that are done by UEFI Secure Boot technology and load a compromised software image on the affected device. A compromised software image is any software image that has not been digitally signed by Cisco.

Affected products

Cisco Fmc1000-K9 Bios: before 4.0.1f.0 — fixed in 4.0.1f.0
Cisco Fmc1000-K9 Firmware: before 4.0.2h — fixed in 4.0.2h
Cisco Fmc2500-K9 Bios: before 4.0.1f.0 — fixed in 4.0.1f.0
Cisco Fmc2500-K9 Firmware: before 4.0.2h — fixed in 4.0.2h
Cisco Fmc4500-K9 Bios: before 4.0.1f.0 — fixed in 4.0.1f.0
Cisco Fmc4500-K9 Firmware: before 4.0.2h — fixed in 4.0.2h
Cisco Identity Services Engine: 2.4(0.357), 2.6(0.156)
Cisco Sns-3515-K9 Bios: before 4.0.2d — fixed in 4.0.2d
Cisco Sns-3515-K9 Firmware: before 4.0.2h — fixed in 4.0.2h
Cisco Sns-3595-K9 Bios: before 4.0.2d — fixed in 4.0.2d
Cisco Sns-3595-K9 Firmware: before 4.0.2h — fixed in 4.0.2h
Cisco Sns-3615-K9 Bios: before 4.0.1i — fixed in 4.0.1i
Cisco Sns-3615-K9 Firmware: before 4.0.1g — fixed in 4.0.1g
Cisco Sns-3655-K9 Bios: before 4.0.1i — fixed in 4.0.1i
Cisco Sns-3655-K9 Firmware: before 4.0.1g — fixed in 4.0.1g
Cisco Sns-3695-K9 Bios: before 4.0.1i — fixed in 4.0.1i
Cisco Sns-3695-K9 Firmware: before 4.0.1g — fixed in 4.0.1g
Cisco Tg5004-K9-Rf Bios: before 4.0.2d — fixed in 4.0.2d
Cisco Tg5004-K9-Rf Firmware: before 4.0.2h — fixed in 4.0.2h
Cisco Tg5004-K9 Bios: before 4.0.2d — fixed in 4.0.2d
Cisco Tg5004-K9 Firmware: before 4.0.2h — fixed in 4.0.2h
Cisco Unified Computing System (Managed): 3.2(3h)c

How to fix

Upgrade to a fixed version: Cisco Fmc1000-K9 Bios 4.0.1f.0; Cisco Fmc1000-K9 Firmware 4.0.2h; Cisco Fmc2500-K9 Bios 4.0.1f.0; Cisco Fmc2500-K9 Firmware 4.0.2h; Cisco Fmc4500-K9 Bios 4.0.1f.0; Cisco Fmc4500-K9 Firmware 4.0.2h; Cisco Sns-3515-K9 Bios 4.0.2d; Cisco Sns-3515-K9 Firmware 4.0.2h; Cisco Sns-3595-K9 Bios 4.0.2d; Cisco Sns-3595-K9 Firmware 4.0.2h; Cisco Sns-3615-K9 Bios 4.0.1i; Cisco Sns-3615-K9 Firmware 4.0.1g. Check the vendor advisory for mitigations.

References

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