However, most of the exploits you'll find in QEMU are against configurations that are never used in real world virtualization scenarios where guests are untrusted. You can recognize them because hardware not commonly used with untrusted guests does not get a CVE.

For a while, slirp was the remaining major issue because it was used way beyond the original intention. But now it's been tamed and there's also passt, a much higher performance and much more secure implementation of user-mode networking.