http://git.savannah.gnu.org/gitweb/?p=gnutls.git;a=commit;h=422214868061370aeeb0ac9cd0f021a5c350a57d

--- lib/gnutls_cipher.c	2009-11-02 10:30:39.000000000 +0000
+++ lib/gnutls_cipher.c.oden	2012-03-27 08:24:14.000000000 +0000
@@ -501,14 +501,13 @@ _gnutls_ciphertext2compressed (gnutls_se
 	{
 	  ciphertext.size -= blocksize;
 	  ciphertext.data += blocksize;
-
-	  if (ciphertext.size == 0)
-	    {
-	      gnutls_assert ();
-	      return GNUTLS_E_DECRYPTION_FAILED;
-	    }
 	}
 
+      if (ciphertext.size < hash_size)
+        {
+          gnutls_assert ();
+          return GNUTLS_E_DECRYPTION_FAILED;
+        }
       pad = ciphertext.data[ciphertext.size - 1] + 1;	/* pad */
 
       if ((int) pad > (int) ciphertext.size - hash_size)