Xorg-x11-server: heap buffer overread/data leakage in procxigetselectedevents

A heap-based buffer over-read vulnerability was found in the X.org server's ProcXIGetSelectedEvents() function. This issue occurs when byte-swapped length values are used in replies, potentially leading to memory leakage and segmentation faults, particularly when triggered by a client with a different endianness. This vulnerability could be exploited by an attacker to cause the X server to read heap memory values and then transmit them back to the client until encountering an unmapped page, resulting in a crash. Despite the attacker's inability to control the specific memory copied into the replies, the small length values typically stored in a 32-bit integer can result in significant attempted out-of-bounds reads.