Made public today was CVE-2023-43785 as an out-of-bounds memory access within the libX11 code that has been around since 1996. A second libX11 flaw is stack exhaustion from infinite recursion within the PutSubImage() function of libX11… This vulnerability has been around since X11R2 in February of 1988.
Due to these issues coming to light, libX11 1.8.7 and libXpm 3.5.17 were released today with the necessary security fixes. More details on these latest X.Org security vulnerabilities via today’s X.Org security advisory.
FYI, Ubuntu/Pop!_OS have already pushed out updates.