A flaw was found in QPDF through 8.0.2. libqpdf.a mishandles certain "expected dictionary key but found non-name object" cases, allowing remote attackers to cause a denial of service (stack exhaustion), related to the QPDFObjectHandle and QPDF_Dictionary classes.
Created qpdf tracking bugs for this issue:
Affects: fedora-all [bug 1566757]
Affects: epel-6 [bug 1566758]
Upstream patch https://github.com/qpdf/qpdf/commit/b4d6cf6836ce025ba1811b7bbec52680c7204223
qpdf-7.1.1-5.fc28 has been pushed to the Fedora 28 stable repository. If problems still persist, please make note of it in this bug report.