CWE-940: Improper Verification of Source of a Communication Channel
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Edit Custom FilterThe product establishes a communication channel to handle an incoming request that has been initiated by an actor, but it does not properly verify that the request is coming from the expected origin.
When an attacker can successfully establish a communication channel from an untrusted origin, the attacker may be able to gain privileges and access unexpected functionality.
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![]() Languages Class: Not Language-Specific (Undetermined Prevalence) Technologies Class: Mobile (Undetermined Prevalence) Example 1 This Android application will remove a user account when it receives an intent to do so: (bad code)
Example Language: Java
IntentFilter filter = new IntentFilter("com.example.RemoveUser");
MyReceiver receiver = new MyReceiver(); registerReceiver(receiver, filter); public class DeleteReceiver extends BroadcastReceiver { @Override }public void onReceive(Context context, Intent intent) { int userID = intent.getIntExtra("userID"); }destroyUserData(userID); This application does not check the origin of the intent, thus allowing any malicious application to remove a user. Always check the origin of an intent, or create an allowlist of trusted applications using the manifest.xml file. Example 2 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: (bad code)
Example Language: 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; }(bad code)
Example Language: 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"]) { // Make data available back in webview. UIWebView *webView = [self writeDataToView:[URL query]]; return NO; return YES; A call into native code can then be initiated by passing parameters within the URL: (attack code)
Example Language: JavaScript
window.location = examplescheme://method?parameter=value
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.
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While many access control issues involve authenticating the user, this weakness is more about authenticating the actual source of the communication channel itself; there might not be any "user" in such cases.
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