In the Linux kernel, the following vulnerability has been resolved:

net/sched: cls_flow: Dont expose folded kernel pointers

The flow classifier falls back to addr_fold() for fields that are missing
from packet headers. In map mode, userspace controls mask, xor, rshift,
addend and divisor, and can observe the resulting classid through class
statistics. This allows a tc classifier in a user/network namespace to
recover the 32-bit folded value of skb->sk, skb_dst() or skb_nfct().

Align with standard kernel practices for pointer hashing and replace the
XOR folding with a keyed siphash (which is cryptographically secure)