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CWE-939

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CWE-939

Improper Authorization in Handler for Custom URL Scheme

Base
Incomplete

Description

The product uses a handler for a custom URL scheme, but it does not properly restrict which actors can invoke the handler using the scheme.

Mobile platforms and other architectures allow the use of custom URL schemes to facilitate communication between applications. In the case of iOS, this is the only method to do inter-application communication. The implementation is at the developer's discretion which may open security flaws in the application. An example could be potentially dangerous functionality such as modifying files through a custom URL scheme.

Common Consequences

Scope

Access Control
Other

Impact

Gain Privileges or Assume Identity, Varies by Context, Bypass Protection Mechanism

Potential Mitigations

Architecture and Design

Utilize a user prompt pop-up to authorize potentially harmful actions such as those modifying data or dealing with sensitive information. When designing functionality of actions in the URL scheme, consider whether the action should be accessible to all mobile applications, or if an allowlist of applications to interface with is appropriate.

CVE-2013-5725

URL scheme has action replace which requires no user prompt and allows remote attackers to perform undesired actions.

CVE-2013-5726

URL scheme has action follow and favorite which allows remote attackers to force user to perform undesired actions.

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