X.org : Security Vulnerabilities, CVEs, Published In January 2006 (Denial of service)

The XClientMessageEvent struct used in certain components of X.Org 6.8.2 and earlier, possibly including (1) the X server and (2) Xlib, uses a "long" specifier for elements of the l array, which results in inconsistent sizes in the struct on 32-bit versus 64-bit platforms, and might allow attackers to cause a denial of service (application crash) and possibly conduct other attacks.