The current version of UPX inside the F26 branch and most likely rawhide as well complains that LZMA support is not compiled inside the binary and then aborts. -bash-4.4$ sudo upx --best --brute -qq /bin/gcc upx: packer_c.cpp:43: static bool Packer::isValidCompressionMethod(int): Assertion `0 && "Internal error - LZMA not compiled in"' failed. Aborted Here a test output with the commands described above. F25 version works perfectly. By the way 3.9.3 is out, so it would make sense updating as well...
upx-3.93-1.fc26 has been submitted as an update to Fedora 26. https://bodhi.fedoraproject.org/updates/FEDORA-2017-a1d337603d
upx-3.93-1.fc26 has been pushed to the Fedora 26 testing repository. If problems still persist, please make note of it in this bug report. See https://fedoraproject.org/wiki/QA:Updates_Testing for instructions on how to install test updates. You can provide feedback for this update here: https://bodhi.fedoraproject.org/updates/FEDORA-2017-a1d337603d
upx-3.93-1.fc26 has been pushed to the Fedora 26 stable repository. If problems still persist, please make note of it in this bug report.