Angular Expressions - Remote Code Execution

Impact

The vulnerability, reported by GoSecure Inc, allows Remote Code Execution, if you call expressions.compile(userControlledInput) where userControlledInput is text that comes from user input.

This time, the security of the package could be bypassed by using a more complex payload, using a .constructor.constructor technique.

• If running angular-expressions in the browser, an attacker could run any browser script when the application code calls expressions.compile(userControlledInput).
• If running angular-expressions on the server, an attacker could run any Javascript expression, thus gaining Remote Code Execution.

Patches

Users should upgrade to version 1.1.2 of angular-expressions

Workarounds

A temporary workaround might be either to :

• disable user-controlled input that will be fed into angular-expressions in your application

OR

• allow only following characters in the userControlledInput :

if (/^[|a-zA-Z.0-9 :"'+-?]+$/.test(userControlledInput)) {
      var result = expressions.compile(userControlledInput);
}
else {
     result = undefined;
}

References

Removal of angular-expression sandbox

For more information

If you have any questions or comments about this advisory:

• Open an issue in angular-expressions
• Email us

Credits

The issue was reported by Maxime Nadeau from GoSecure, Inc.