Integer Overflow or Wraparound Affecting wayland package, versions *

Note: Versions mentioned in the description apply only to the upstream wayland package and not the wayland package as distributed by Debian. See How to fix? for Debian:11 relevant fixed versions and status.

An internal reference count is held on the buffer pool, incremented every time a new buffer is created from the pool. The reference count is maintained as an int; on LP64 systems this can cause the reference count to overflow if the client creates a large number of wl_shm buffer objects, or if it can coerce the server to create a large number of external references to the buffer storage. With the reference count overflowing, a use-after-free can be constructed on the wl_shm_pool tracking structure, where values may be incremented or decremented; it may also be possible to construct a limited oracle to leak 4 bytes of server-side memory to the attacking client at a time.

• https://security-tracker.debian.org/tracker/CVE-2021-3782
• https://gitlab.freedesktop.org/wayland/wayland/-/issues/224