CVSS2
Attack Vector
NETWORK
Attack Complexity
LOW
Authentication
SINGLE
Confidentiality Impact
COMPLETE
Integrity Impact
COMPLETE
Availability Impact
COMPLETE
AV:N/AC:L/Au:S/C:C/I:C/A:C
CVSS3
Attack Vector
LOCAL
Attack Complexity
LOW
Privileges Required
HIGH
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
HIGH
Integrity Impact
HIGH
Availability Impact
HIGH
CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H
EPSS
Percentile
71.8%
Cisco’s Trust Anchor module (TAm) can be bypassed through manipulating the bitstream of the Field Programmable Gate Array (FPGA). This component handles access control to a hardware component within Cisco’s Secure Boot implementations, which affects multiple products that support this functionality. An authenticated, local attacker could bypass the Secure Boot and make persistent changes to the root trust for software integrity. Additionally, Cisco’s IOS XE web UI improperly sanitizes user-input, and could allow an authenticated, remote attack to execute commands. An authenticated, remote attacker could execute commands as root on the vulnerable device.
CVE-2019-1649: Secure Boot Tampering, also known as Thrangrycat
The logic that handles Cisco’s Secure Boot improperly checks an area of code that manages the Field Programmable Gate Array (FPGA). The secure boot feature is a proprietary FPGA based implementation used for ensuring chain of trust for software. The secure boot can be bypassed by modifying the bitstream of the FPGA, allowing an authenticated, local attacker to make persistent modification to the root of trust for software integrity.
CVE-2019-1862: IOS XE Web UI Command Injection
The web user interface of Cisco IOS XE improperly sanitizes user-supplied input. This could allow an authenticated, remote attacker to execute commands as root on the underlying Linux shell.
A local or remote attacker could write a new firmware image to the TAm. When exploited together, these vulnerabilities could allow a remote, authenticated attacker to remotely and persistently bypass Secure Boot and prevent future software updates to the TAm.
To exploit CVE-2019-1649, an attacker would need to have privileged administrative access to the device. This type of access could be achieved by exploiting the vulnerability described in CVE-2019-1862 or other potential remote command injection vulnerabilities.
CVE-2019-1649
Cisco is in the process of developing and releasing software fixes for all affected platforms. We recommend installing this update when it is available.
CVE-2019-1862
Apply the update from Cisco.
Workaround
CVE-2019-1649
Guidance from Cisco recommends that users refer to the Cisco Guide to Harden Cisco IOS Devices, as it provides information about how to harden the device and secure management access. Implementing the recommendations in this document would likely reduce the attack surface for this vulnerability.
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Updated: May 16, 2019
Affected
We have not received a statement from the vendor.
We are not aware of further vendor information regarding this vulnerability.
Group | Score | Vector |
---|---|---|
Base | 6.8 | AV:L/AC:L/Au:S/C:C/I:C/A:C |
Temporal | 6.8 | E:ND/RL:U/RC:C |
Environmental | 6.8 | CDP:ND/TD:ND/CR:ND/IR:ND/AR:ND |
This document was written by Madison Oliver.
CVE IDs: | CVE-2019-1649, CVE-2019-1862 |
---|---|
Date Public: | 2019-05-13 Date First Published: |
thrangrycat.com/
tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20190513-secureboot
tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20190513-webui
www.cisco.com/c/dam/en_us/about/doing_business/trust-center/docs/trustworthy-technologies-datasheet.pdf
www.cisco.com/c/en/us/support/docs/ip/access-lists/13608-21.html
CVSS2
Attack Vector
NETWORK
Attack Complexity
LOW
Authentication
SINGLE
Confidentiality Impact
COMPLETE
Integrity Impact
COMPLETE
Availability Impact
COMPLETE
AV:N/AC:L/Au:S/C:C/I:C/A:C
CVSS3
Attack Vector
LOCAL
Attack Complexity
LOW
Privileges Required
HIGH
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
HIGH
Integrity Impact
HIGH
Availability Impact
HIGH
CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H
EPSS
Percentile
71.8%