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ID

CWE-1253: Incorrect Selection of Fuse Values

Weakness ID: 1253
Abstraction: Base
Structure: Simple
Status: Draft
Presentation Filter:
+ Description
The logic level used to set a system to a secure state relies on a fuse being unblown. An attacker can set the system to an insecure state merely by blowing the fuse.
+ Extended Description

Fuses are often used to store secret data, including security configuration data. When not blown, a fuse is considered to store a logic 0, and, when blown, it indicates a logic 1. Fuses are generally considered to be one-directional, i.e., once blown to logic 1, it cannot be reset to logic 0. However, if the logic used to determine system-security state (by leveraging the values sensed from the fuses) uses negative logic, an attacker might blow the fuse and drive the system to an unsecure state.

+ Relationships

The table(s) below shows the weaknesses and high level categories that are related to this weakness. These relationships are defined as ChildOf, ParentOf, MemberOf and give insight to similar items that may exist at higher and lower levels of abstraction. In addition, relationships such as PeerOf and CanAlsoBe are defined to show similar weaknesses that the user may want to explore.

+ Relevant to the view "Research Concepts" (CWE-1000)
NatureTypeIDName
ChildOfPillarPillar - a weakness that is the most abstract type of weakness and represents a theme for all class/base/variant weaknesses related to it. A Pillar is different from a Category as a Pillar is still technically a type of weakness that describes a mistake, while a Category represents a common characteristic used to group related things.693Protection Mechanism Failure
+ Relevant to the view "Hardware Design" (CWE-1194)
NatureTypeIDName
MemberOfCategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.1199General Circuit and Logic Design Concerns
+ Modes Of Introduction

The different Modes of Introduction provide information about how and when this weakness may be introduced. The Phase identifies a point in the life cycle at which introduction may occur, while the Note provides a typical scenario related to introduction during the given phase.

PhaseNote
Architecture and Design
Implementation
+ Applicable Platforms
The listings below show possible areas for which the given weakness could appear. These may be for specific named Languages, Operating Systems, Architectures, Paradigms, Technologies, or a class of such platforms. The platform is listed along with how frequently the given weakness appears for that instance.

Languages

Class: Language-Independent (Undetermined Prevalence)

Operating Systems

Class: OS-Independent (Undetermined Prevalence)

Architectures

Class: Architecture-Independent (Undetermined Prevalence)

Technologies

Class: Technology-Independent (Undetermined Prevalence)

+ Common Consequences

The table below specifies different individual consequences associated with the weakness. The Scope identifies the application security area that is violated, while the Impact describes the negative technical impact that arises if an adversary succeeds in exploiting this weakness. The Likelihood provides information about how likely the specific consequence is expected to be seen relative to the other consequences in the list. For example, there may be high likelihood that a weakness will be exploited to achieve a certain impact, but a low likelihood that it will be exploited to achieve a different impact.

ScopeImpactLikelihood
Access Control
Authorization

Technical Impact: Bypass Protection Mechanism; Gain Privileges or Assume Identity

Availability

Technical Impact: DoS: Crash, Exit, or Restart

Confidentiality

Technical Impact: Read Memory

Integrity

Technical Impact: Modify Memory; Execute Unauthorized Code or Commands

+ Demonstrative Examples

Example 1

A chip implements a secure boot and uses the sensed value of a fuse "do_secure_boot" to determine whether to perform a secure boot or not. If this fuse value is "0", the system performs secure boot. Otherwise, it does not perform secure boot.

An attacker blows the "do_secure_boot" fuse to "1". After reset, the attacker loads a custom bootloader, and, since the fuse value is now "1", the system does not perform secure boot, and the attacker can execute their custom firmware image.

Since by default, a fuse-configuration value is a "0", an attacker can blow it to a "1" with inexpensive hardware.

If the logic is reversed, an attacker cannot easily reset the fuse. Note that, with specialized and expensive equipment, an attacker with full physical access might be able to "unblow" the fuse value to a "0".

+ Potential Mitigations

Phase: Architecture and Design

Logic should be designed in a way that blown fuses do not put the product into an insecure state that can be leveraged by an attacker.
+ Notes

Maintenance

This entry is still under development and will continue to see updates and content improvements.
+ References
[REF-1080] Christopher Tarnovsky. "Security Failures in Secure Devices". <https://www.blackhat.com/presentations/bh-europe-08/Tarnovsky/Presentation/bh-eu-08-tarnovsky.pdf>.
+ Content History
+ Submissions
Submission DateSubmitterOrganization
2019-10-15Arun Kanuparthi, Hareesh Khattri, Parbati Kumar Manna, Narasimha Kumar V MangipudiIntel Corporation
+ Modifications
Modification DateModifierOrganization
2020-08-20CWE Content TeamMITRE
updated Applicable_Platforms, Demonstrative_Examples, Description
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Page Last Updated: August 20, 2020