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Sun JDK image parsing vulnerabilities



Hi,

A couple more JPEG ICC parsing bugs were fixed in the latest JDK updates.

Full technical details:
http://scary.beasts.org/security/CESA-2007-005.html

The most interesting part is the faulty code:
  Limit = SpGetUInt32 (Buf);
...
  UInt16Ptr = (KpUInt16_t *)SpMalloc (Limit * (KpInt32_t)sizeof (*UInt16Ptr));
...
  for (Index = 0; Index < Limit; Index++)
    *UInt16Ptr++ = SpGetUInt16 (Buf);
...

And the image to trigger:
http://scary.beasts.org/misc/jdk/evilicc2.jpg

Normally, the heap overflow would just terminate the process as the
copy length is kind of wild. However, JDK installs a SEGV handler
which accesses a lot of (potentially trashed) memory in the process of
putting together a meaningful crash dump. It's quite likely that this
makes the condition exploitable as per a previous bug in this area:
http://scary.beasts.org/security/CESA-2006-004.html

Blog post for all of the above:
http://scarybeastsecurity.blogspot.com/2008/03/sun-jdk-image-parsing-vulnerabilities.html

Cheers
Chris