KubeVirt Arbitrary Container File Read

Vulnerability Description

KubeVirt is a virtual machine management add-on for Kubernetes. Prior to 1.5.3 and 1.6.1, a vulnerability was discovered that allows a VM to read arbitrary files from the virt-launcher pod's file system. This issue stems from improper symlink handling when mounting PVC disks into a VM. Specifically, if a malicious user has full or partial control over the contents of a PVC, they can create a symbolic link that points to a file within the virt-launcher pod's file system. Since libvirt can treat regular files as block devices, any file on the pod's file system that is symlinked in this way can be mounted into the VM and subsequently read. Although a security mechanism exists where VMs are executed as an unprivileged user with UID 107 inside the virt-launcher container, limiting the scope of accessible resources, this restriction is bypassed due to a second vulnerability. The latter causes the ownership of any file intended for mounting to be changed to the unprivileged user with UID 107 prior to mounting. As a result, an attacker can gain access to and read arbitrary files located within the virt-launcher pod's file system or on a mounted PVC from within the guest VM. This vulnerability is fixed in 1.5.3 and 1.6.1.

References

• https://github.com/kubevirt/kubevirt/security/advisories/GHSA-qw6q-3pgr-5cwq
• https://github.com/kubevirt/kubevirt/commit/09eafa068ec01eca0e96ebafeeb9522a878dbf64
• https://github.com/kubevirt/kubevirt/commit/9dc798cb1efe924a9a2b97b6e016452dec5e3849
• https://github.com/kubevirt/kubevirt/commit/a81b27d4600cf654274dd197119658382affdb08