\documentclass[
11pt,
a4paper,
twoside,
openright,
]{scrbook}
\usepackage{tikz}
\usetikzlibrary{babel}
\usepackage{lipsum}
\usepackage{fancyhdr}
\newcommand\tikzmark[1]{%
\tikz[remember picture,overlay] \coordinate (#1);}
\pagestyle{fancy}
\fancyhf{}
\fancyhead[LE]{\leftmark}
\fancyhead[RO]{\rightmark}
\renewcommand*{\sectionmark}[1]{%
\markright{\protect\tikzmark{starta}\thesection~#1%
\protect\begin{tikzpicture}[remember picture,overlay]
\protect\draw
([yshift=-5pt]starta) --