If this code is compiled:

import java.io.IOException;

public class FunWithMultiCatch {
  public static void main(String[] args) {
    Runnable r = () -> {
      try {
        Object o = null;
        o.getClass();
        throw new IOException();
      } catch(IOException | IllegalArgumentException e) {
        System.out.println("KO !");
      } catch(RuntimeException e) {
        System.out.println("OK !");
      }
    };
    r.run();
  }
}

javac generates this code:

private static void lambda$main$0();
    descriptor: ()V
    flags: ACC_PRIVATE, ACC_STATIC, ACC_SYNTHETIC
    Code:
      stack=2, locals=1, args_size=0
         0: aconst_null
         1: astore_0
         2: aload_0
         3: invokevirtual #4 // Method java/lang/Object.getClass:()Ljava/lang/Class;
         6: pop
         7: new #5 // class java/io/IOException
        10: dup
        11: invokespecial #6 // Method java/io/IOException."<init>":()V
        14: athrow
        15: astore_0
        16: getstatic #8 // Field java/lang/System.out:Ljava/io/PrintStream;
        19: ldc #9 // String KO !
        21: invokevirtual #10 // Method java/io/PrintStream.println:(Ljava/lang/String;)V
        24: goto 36
        27: astore_0
        28: getstatic #8 // Field java/lang/System.out:Ljava/io/PrintStream;
        31: ldc #12 // String OK !
        33: invokevirtual #10 // Method java/io/PrintStream.println:(Ljava/lang/String;)V
        36: return
      Exception table:
         from to target type
             0 15 15 Class java/lang/Exception <----- this will capture all exceptions.
             0 15 27 Class java/lang/RuntimeException

if the original code is modified to:

import java.io.IOException;

class FunWithMultiCatch {
  public static void main(String[] args) {
      try {
        Object o = null;
        o.getClass();
        throw new IOException();
      } catch(IOException | IllegalArgumentException e) {
        System.out.println("KO !");
      } catch(RuntimeException e) {
        System.out.println("OK !");
      }
  }
}

then we obtain this exception table:

    Exception table:
         from to target type
             0 15 15 Class java/io/IOException
             0 15 15 Class java/lang/IllegalArgumentException
             0 15 27 Class java/lang/RuntimeException

reported in lambda-dev: http://mail.openjdk.java.net/pipermail/lambda-dev/2014-March/011940.html