The embedded libexpat library is vulnerable to a stack overflow
due to uncontrolled recursion when processing deeply nested XML
entities. This can cause the application to crash, resulting in
a denial of service (DoS) or potentially leading to memory
corruption, depending on the user's environment and how the
library is used. The issue is triggered by supplying a specially
crafted XML document designed to create a long chain of recursive
entities.
libexpat addressed this upstream in
https://github.com/libexpat/libexpat/pull/973
but the embedded copy within xmlrpc-c is so old there is no chance
of applying this without rebasing it. Instead a recursion counter
is added to the parser to limit the depth.
Resolves: RHEL-57536
