GHSA-m38g-vww2-mvgx

Summary

A vulnerability in the Linux kernel's algif_aead subsystem (CVE-2026-31431, "copy.fail") allows an unprivileged container workload to corrupt arbitrary file page-cache pages via the AF_ALG crypto interface and splice(). On Talos Linux, this vulnerability can be chained into a complete node compromise: an attacker who can schedule a pod on a worker node can, without any elevated Kubernetes permissions, achieve arbitrary code execution as root on the host (by poisoning a binary inside a privileged pod, or poisoning a binary which runs with elevated privileges like a CNI binary), access host filesystem, including node secrets.

The exploit does not require kernel debugging, race conditions, or any prior privileges beyond the ability to create a pod.

Impact

An attacker with the ability to deploy a Kubernetes pod on an affected node can:

1. Corrupt the page-cache of /usr/sbin/nft in the containerd snapshot layer shared between the attacker's pod and the kube-proxy DaemonSet. Because containerd reuses XFS page-cache pages across overlayfs mounts sharing the same lower layer, the corruption is immediately visible to all containers using that image layer — including privileged system DaemonSets.
2. Execute arbitrary code inside kube-proxy — a privileged DaemonSet running on every node with all Linux capabilities (privileged: true) and host network access — the next time kube-proxy invokes nft as part of its nftables reconciliation loop (typically within seconds).
3. At this point, an attacker achieved code execution inside a privileged pod, which allows to escape to the host.
4. Same attack can be planted by infiltrating other binaries running as privileged, for example a CNI plugin.

Patches

Upgrade to Talos v1.13.0 or Talos v1.12.7 which ships Linux kernel 6.18.25. The kernel fix for CVE-2026-31431 (algif_aead in-place optimization revert) was committed upstream in Linux 6.18.22 and is included in all Talos releases from v1.13.0 and Talos...