FULL PRODUCT VERSION :
java version "1.7.0_25"
Java(TM) SE Runtime Environment (build 1.7.0_25-b17)
Java HotSpot(TM) Client VM (build 23.25-b01, mixed mode, sharing)

ADDITIONAL OS VERSION INFORMATION :
Microsoft Windows [Version 6.1.7601]

A DESCRIPTION OF THE PROBLEM :
In the ImageIO method
"write(RenderedImage im, String formatName, File output) throws IOException"
ImageOutputStream is created through code
"stream = createImageOutputStream(output);"

In the finally block stream is closed without null check
"finally { stream.close(); }"
But in the createImageOutputStream method there is a code like
"try {
iter = theRegistry.getServiceProvidersImageOutputStreamSpi.class,true);
 } catch (IllegalArgumentException e) { return null; } "

so the catch block returns null which will make "stream=null" in the "write" method mentioned above.

This will throw NullPointerException in the stream.close() call.

Please put a null check in the finally block
"if(stream!= null) stream.close();"

Not just this specific write method on other write() and read() methods also we are not handling NPE properly.
REPRODUCIBILITY :
This bug can be reproduced occasionally.