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

ip gre: Reject enabling collect metadata through changelink

ipgre netlink parms() can enable collect md on an existing GRE, GRETAP or ERSPAN device. Unlike newlink, changelink does not enforce metadata tunnel uniqueness. Converting a non-metadata device can therefore replace the metadata receive entry for another device of the same type in the same netns. Deleting either device then clears the shared entry, breaking metadata receive lookup for the surviving device.

If parameter validation fails after collect md is set, deleting the modified device can also clear an entry it never owned.

Reject enabling metadata mode in both changelink callbacks before any encapsulation or tunnel parameters are modified. Allow requests that repeat the metadata attribute on an existing metadata device.