Code-reuse attacks represent the state-of-the-art in exploiting memory safety vulnerabilities. Control-flow integrity techniques offer a promising direction for preventing codereuse attacks, but these attacks are resilient against imprecise and heuristic-based detection and prevention mechanisms.In this work, we propose a new context-sensitive controlflow integrity system (Hurdle) that guarantees pairwise gadgets cannot be chained in a code-reuse attack. Hurdle improves upon prior techniques by using SMT constraint solving to ensure that indirect control flow transfers cannot be maliciously redirected to execute gadget chains. At the same time, Hurdle's security policy is flexible enough that benign executions are only rarely mischaracterized as malicious. When such mischaracterizations occur, Hurdle can generalize its constraint solving to avoid these mischaracterizations at low marginal cost.We propose architecture extensions for Hurdle which consist of an extended branch history register and new instructions. Thanks to its hardware support, Hurdle enforces a context-sensitive control-flow integrity policy with 1.02% average runtime overhead.• Security and privacy → Hardware security implementation; Malware and its mitigation.