The recent BadRAM attack against AMD's Secure Encrypted Virtualisation works by changing something in the memory DIMM's SPD (Serial Presence Detect) EEPROM firmware causing out to report twice as much RAM as the DIMM really has. Chaining this up with a bunch of other neat tricks they gain access to protected memory that the CPU is _supposed_ to prevent.

I don't think there's a public working exploits (yet?), but it can "likely" in some cases (depending on the DIMMS you have installed) be done without hardware access, purely through software:

"In some cases, with certain DIMM models that don't adequately lock down the chip, the modification can likely be done through software."

https://arstechnica.com/information-technology/2024/12/new-b...

So yeah, it's possible for a hacker to flash malware onto your DIMMs...

(Whether that's a thing you need to care about is a good question. This isn't something a driveway script kiddie is gonna do after he p0wns your WordPress site with vulnerable plugins. But if you're running a dark web drug market on commercially hosted cloud servers and a powerful enough Three Letter Agency becomes intersted in you...)