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Exposed Dangerous Method or Function

Incomplete Base
Structure: Simple
Description

The product provides an Applications Programming Interface (API) or similar interface for interaction with external actors, but the interface includes a dangerous method or function that is not properly restricted.

Extended Description

This weakness can lead to a wide variety of resultant weaknesses, depending on the behavior of the exposed method. It can apply to any number of technologies and approaches, such as ActiveX controls, Java functions, IOCTLs, and so on. The exposure can occur in a few different ways: - The function/method was never intended to be exposed to outside actors. - The function/method was only intended to be accessible to a limited set of actors, such as Internet-based access from a single web site.

Common Consequences 1
Scope: IntegrityConfidentialityAvailabilityAccess ControlOther

Impact: Gain Privileges or Assume IdentityRead Application DataModify Application DataExecute Unauthorized Code or CommandsOther

Exposing critical functionality essentially provides an attacker with the privilege level of the exposed functionality. This could result in the modification or exposure of sensitive data or possibly even execution of arbitrary code.
Detection Methods 1
Automated Static AnalysisHigh
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.)
Potential Mitigations 2
Phase: Architecture and Design
If you must expose a method, make sure to perform input validation on all arguments, limit access to authorized parties, and protect against all possible vulnerabilities.
Phase: Architecture and DesignImplementation

Strategy: Attack Surface Reduction

Identify all exposed functionality. Explicitly list all functionality that must be exposed to some user or set of users. Identify which functionality may be: - accessible to all users - restricted to a small set of privileged users - prevented from being directly accessible at all Ensure that the implemented code follows these expectations. This includes setting the appropriate access modifiers where applicable (public, private, protected, etc.) or not marking ActiveX controls safe-for-scripting.
Demonstrative Examples 4
In the following Java example the method removeDatabase will delete the database with the name specified in the input parameter.

Code Example:

Bad
Java
java
The method in this example is declared public and therefore is exposed to any class in the application. Deleting a database should be considered a critical operation within an application and access to this potentially dangerous method should be restricted. Within Java this can be accomplished simply by declaring the method private thereby exposing it only to the enclosing class as in the following example.

Code Example:

Good
Java
java

ID : DX-109

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:

Code Example:

Bad
Java


// Android*
@Override
public boolean shouldOverrideUrlLoading(WebView view, String url){
```
if (url.substring(0,14).equalsIgnoreCase("examplescheme:")){
if(url.substring(14,25).equalsIgnoreCase("getUserInfo")){
writeDataToView(view, UserData);
return false;
}
else{
return true;
}
}
}


Code Example:
Bad
Objective-C


// iOS*
-(BOOL) webView:(UIWebView *)exWebView shouldStartLoadWithRequest:(NSURLRequest *)exRequest navigationType:(UIWebViewNavigationType)exNavigationType
{
```
NSURL *URL = [exRequest URL];
if ([[URL scheme] isEqualToString:@"exampleScheme"])
{
NSString *functionString = [URL resourceSpecifier];
if ([functionString hasPrefix:@"specialFunction"])
{


objective-c
A call into native code can then be initiated by passing parameters within the URL:
Code Example:
Attack
JavaScript
javascript
Because the application does not check the source, a malicious website loaded within this WebView has the same access to the API as a trusted site.
This application uses a WebView to display websites, and creates a Javascript interface to a Java object to allow enhanced functionality on a trusted website:
Code Example:
Bad
Java
java
Before Android 4.2 all methods, including inherited ones, are exposed to Javascript when using addJavascriptInterface(). This means that a malicious website loaded within this WebView can use reflection to acquire a reference to arbitrary Java objects. This will allow the website code to perform any action the parent application is authorized to.
For example, if the application has permission to send text messages:
Code Example:
Attack
JavaScript
javascript
This malicious script can use the userInfoObject object to load the SmsManager object and send arbitrary text messages to any recipient.
After Android 4.2, only methods annotated with @JavascriptInterface are available in JavaScript, protecting usage of getClass() by default, as in this example:
Code Example:
Bad
Java
java
This code is not vulnerable to the above attack, but still may expose user info to malicious pages loaded in the WebView. Even malicious iframes loaded within a trusted page may access the exposed interface:
Code Example:
Attack
JavaScript
javascript
This malicious code within an iframe is able to access the interface object and steal the user's data.
  
Observed Examples 2
CVE-2007-6382arbitrary Java code execution via exposed method
CVE-2007-1112security tool ActiveX control allows download or upload of files
  
References 2
Developing Secure ActiveX Controls
Microsoft
13-04-2005
https://learn.microsoft.com/en-us/previous-versions//ms533046(v=vs.85)?redirectedfrom=MSDN(2023-04-07)
ID: REF-503
How to stop an ActiveX control from running in Internet Explorer
Microsoft
https://support.microsoft.com/en-us/help/240797/how-to-stop-an-activex-control-from-running-in-internet-explorer(2023-04-07)
ID: REF-510
 
  
  
 
 
Likelihood of Exploit 
 
 
 
 Low 
 
 
  
 
 
Applicable Platforms 
 
 
 
 
 
Languages:
 
 
 Not Language-Specific : Undetermined 
  
  
 
 
 
  
 
 
Modes of Introduction 
 
 
 
 
 
  Architecture and Design  
 
  Implementation  
 
 
 
  
Related Attack Patterns 
        
 
 
Related Weaknesses 
 
 
 
 
  ChildOf:
 Improper Access Control (CWE-284) 
 
 
 
   
Notes 
Research GapUnder-reported and under-studied. This weakness could appear in any technology, language, or framework that allows the programmer to provide a functional interface to external parties, but it is not heavily reported. In 2007, CVE began showing a notable increase in reports of exposed method vulnerabilities in ActiveX applications, as well as IOCTL access to OS-level resources. These weaknesses have been documented for Java applications in various secure programming sources, but there are few reports in CVE, which suggests limited awareness in most parts of the vulnerability research community.