Rowhammer is a hardware attack against DRAM. By repeatedly reading or writing memory in the same area, an attacker can create electrical disturbance in nearby rows and sometimes flip individual bits. This is not a normal software vulnerability: the exploit targets how memory cells physically behave under heavy access patterns.
Bit flips matter because even a single corrupted bit can change permissions, break cryptographic material, corrupt page tables, or crash a system. In real attacks, Rowhammer is used to turn memory corruption into privilege escalation or denial of service. Defenders reduce risk with ECC, memory refresh mitigations, target-row protections, access throttling, and careful monitoring for unusual memory patterns, but no single control makes DRAM immune.