Memory injection occurs when malicious code is written into the memory space of a running process, allowing it to execute without writing anything to disk. This is often used in fileless malware attacks, making detection harder.
A (privilege escalation) describes a race condition, not memory injection.
B (unexpected data causing execution) describes a buffer overflow attack, not memory injection.
D (overwriting an executable) is a persistence technique, but it is not an example of in-memory injection.
Reference:
CompTIA Security+ SY0-701 Official Study Guide, Threats, Vulnerabilities, and Mitigations domain.