A Security Update (SU) is a targeted software update that fixes specific security vulnerabilities without delivering a broad feature change or full product refresh. In enterprise systems, SUs are often smaller and faster to deploy than cumulative updates, making them a key part of patch management and exposure reduction.
SUs matter because attackers frequently exploit known flaws soon after disclosure, especially in Internet-facing services and admin platforms. By applying an SU quickly, defenders can close a vulnerable code path, reduce the chance of remote code execution or privilege escalation, and limit an attacker’s window of opportunity. In practice, SUs appear in vendor patch cycles, emergency out-of-band fixes, and hardening guidance for products such as email servers, identity systems, and web applications. Security teams track them closely because delaying an SU can leave a fully supported system exposed even when no new features are needed.