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.
View on MITREMobile 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.
No consequence information available for this CWE.
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.
No detection method information available for this CWE.
This iOS application uses a custom URL scheme. The replaceFileText action in the URL scheme allows an external application to interface with the file incomingMessage.txt and replace the contents with the text field of the query string.
External Application
This iOS application uses a custom URL scheme. The replaceFileText action in the URL scheme allows an external application to interface with the file incomingMessage.txt and replace the contents with the text field of the query string.
External Application
This iOS application uses a custom URL scheme. The replaceFileText action in the URL scheme allows an external application to interface with the file incomingMessage.txt and replace the contents with the text field of the query string.
External Application
These Android and iOS applications intercept URL loading within a WebView and perform special actions if a particular URL scheme is used, thus allowing the Javascript within the WebView to communicate with the application:
A call into native code can then be initiated by passing parameters within the URL:
These Android and iOS applications intercept URL loading within a WebView and perform special actions if a particular URL scheme is used, thus allowing the Javascript within the WebView to communicate with the application:
A call into native code can then be initiated by passing parameters within the URL:
These Android and iOS applications intercept URL loading within a WebView and perform special actions if a particular URL scheme is used, thus allowing the Javascript within the WebView to communicate with the application:
A call into native code can then be initiated by passing parameters within the URL:
URL scheme has action replace which requires no user prompt and allows remote attackers to perform undesired actions.
View DetailsURL scheme has action follow and favorite which allows remote attackers to force user to perform undesired actions.
View DetailsNo relationship information available for this CWE.
CWE-939: Improper Authorization in Handler for Custom URL Scheme is a Common Weakness Enumeration (CWE) entry maintained by MITRE. 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.
Recommended mitigations for CWE-939 include: 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.
MITRE documents real CVEs mapped to CWE-939, including CVE-2013-5725 and CVE-2013-5726. You can look up the full details of each CVE, including CVSS scores and remediation guidance, on our CVE Lookup tool.
A CWE (Common Weakness Enumeration) like CWE-939 describes a category of software weakness — the underlying flaw type. A CVE (Common Vulnerabilities and Exposures) identifies a specific, real-world vulnerability in a particular product. In short, a CWE is the kind of mistake, and a CVE is an instance of that mistake being found in software.