CVE 2017-12595
The tokenizer in QPDF 6.0.0 and 7.0.b1 is recursive for arrays and dictionaries, which allows remote attackers to cause a denial of service (stack consumption and segmentation fault) or possibly have unspecified other impact via a PDF document with a deep data structure, as demonstrated by a crash in QPDFObjectHandl
See the 
CVE page on Mitre.org
for more details.
