CVE-2020-29479

An issue was discovered in Xen through 4.14.x. In the Ocaml xenstored
implementation, the internal representation of the tree has special cases
for the root node, because this node has no parent. Unfortunately,
permissions were not checked for certain operations on the root node.
Unprivileged guests can get and modify permissions, list, and delete the
root node. (Deleting the whole xenstore tree is a host-wide denial of
service.) Achieving xenstore write access is also possible. All systems
using oxenstored are vulnerable. Building and using oxenstored is the
default in the upstream Xen distribution, if the Ocaml compiler is
available. Systems using C xenstored are not vulnerable.

Notes