In OISF LibHTP before 0.5.31, as used in Suricata 4.1.4 and other products, an HTTP protocol parsing error causes the httpheader signature to not alert on a response with a single \r\n ending.
htpparseauthorizationdigest in htpparsers.c in LibHTP 0.5.26 allows remote attackers to cause a heap-based buffer over-read via an authorization digest header.
libhtp 0.5.15 allows remote attackers to cause a denial of service (NULL pointer dereference).