CWE-926 Detail

The Android application exports a component for use by other applications, but does not properly restrict which applications can launch the component or access the data it contains.

The attacks and consequences of improperly exporting a component may depend on the exported component:

• If access to an exported Activity is not restricted, any application will be able to launch the activity. This may allow a malicious application to gain access to sensitive information, modify the internal state of the application, or trick a user into interacting with the victim application while believing they are still interacting with the malicious application.
• If access to an exported Service is not restricted, any application may start and bind to the Service. Depending on the exposed functionality, this may allow a malicious application to perform unauthorized actions, gain access to sensitive information, or corrupt the internal state of the application.
• If access to a Content Provider is not restricted to only the expected applications, then malicious applications might be able to access the sensitive data. Note that in Android before 4.2, the Content Provider is automatically exported unless it has been explicitly declared as NOT exported.

Background Details

There are three types of components that can be exported in an Android application.

• An Activity is an application component that provides a UI for users to interact with. A typical application will have multiple Activity screens that perform different functions, such as a main Activity screen and a separate settings Activity screen.
• A Service is an application component that is started by another component to execute an operation in the background, even after the invoking component is terminated. Services do not have a UI component visible to the user.
• The Content Provider mechanism can be used to share data with other applications or internally within the same application.

Modes Of Introduction

Architecture and Design

Applicable Platforms

Language

Class: Not Language-Specific (Undetermined)

Technologies

Class: Mobile (Undetermined)

Common Consequences

Potential Mitigations

Phases : Build and Compilation
If they do not need to be shared by other applications, explicitly mark components with android:exported="false" in the application manifest.
Phases : Build and Compilation
If you only intend to use exported components between related apps under your control, use android:protectionLevel="signature" in the xml manifest to restrict access to applications signed by you.
Phases : Build and Compilation // Architecture and Design
Limit Content Provider permissions (read/write) as appropriate.
Phases : Build and Compilation // Architecture and Design
Limit Content Provider permissions (read/write) as appropriate.

Detection Methods

Automated Static Analysis

Automated static analysis, commonly referred to as Static Application Security Testing (SAST), can find some instances of this weakness by analyzing source code (or binary/compiled code) without having to execute it. Typically, this is done by building a model of data flow and control flow, then searching for potentially-vulnerable patterns that connect "sources" (origins of input) with "sinks" (destinations where the data interacts with external components, a lower layer such as the OS, etc.)
Effectiveness : High

Vulnerability Mapping Notes

Justification : This CWE entry is at the Variant level of abstraction, which is a preferred level of abstraction for mapping to the root causes of vulnerabilities.
Comment : Carefully read both the name and description to ensure that this mapping is an appropriate fit. Do not try to 'force' a mapping to a lower-level Base/Variant simply to comply with this preferred level of abstraction.

References

REF-923

Security Tips
Android Open Source Project.
https://developer.android.com/training/articles/security-tips#ContentProviders

Submission

Modifications