It was discovered by the SUSE security team that it was possible,
in some cases, for clients to overwrite headers set by the server,
resulting in a medium level security issue. CVE-2015-7519 has been
assigned to this issue.
Affected use-cases:
Header overwriting may occur if all of the following conditions are met:
- Apache integration mode, or standalone+builtin engine without
a filtering proxy
- Ruby or Python applications only (Passenger 5); or any
application (Passenger 4)
- The app depends on a request header containing a dash (-)
- The header is supposed to be trusted (set by the server)
- The client correctly guesses the header name
This vulnerability has been fixed by filtering out client headers
that do not consist of alphanumeric/dash characters (Nginx already
did this, so Passenger+Nginx was not affected). If your application
depends on headers that don't conform to this, you can add a
workaround in Apache specifically for those to convert them to a
dash-based format.