Linux kernel (netfilter x_tables): Heap out-of-bounds write in xt_compat_target_from_user()

CVE-2021-22555Kernel, userspace & hypervisorKnown exploitedcurated

Impact

Heap out-of-bounds write in xt_compat_target_from_user(); reliable container escape via unprivileged userns + CAP_NET_ADMIN [KEV]

Who can reach it

Any tenant process in a container with a user namespace

What to do

Livepatchable; otherwise drain + reboot. Compensating control: disable unprivileged user namespaces (kernel.unprivileged_userns_clone=0) - breaks rootless Podman/Apptainer, which many HPC tenants rely on

References

https://access.redhat.com/security/cve/CVE-2021-22555

This entry is curated: imported from vendor advisories with machine assistance, not yet individually verified. Confirm against your vendor's advisory before acting, and report anything wrong.