Rowhammer attacks have been demonstrated over time by compromising the Linux kernel, breaking cloud isolation, rooting mobile devices, taking control of web browsers, targeting server applications over the network, or extracting sensitive info stored in RAM. Researchers from VUSec (Systems and Network Security Group at VU Amsterdam) found that it is easy to flip the bits after understanding how the mitigation works. The vulnerability is worse on DDR4 chips than on DDR3 because of difference in tolerated row activation counts, which is higher for the latter.
Source: https://www.bleepingcomputer.com/news/security/ddr4-memory-still-at-rowhammer-risk-new-method-bypasses-fixes/