Executive brief
A vulnerability in the underlying Linux kernel allows an attacker with basic access to a Kubernetes cluster to take full control of the host server. By deploying a standard container, an attacker can corrupt shared system files used by high-privilege background services, leading to unauthorized code execution as a root user. This could result in the theft of sensitive node secrets, access to the host filesystem, and a complete compromise of the affected infrastructure.
Technical details
A vulnerability in the Linux kernel's algif_aead subsystem (CVE-2026-31431, known as 'copy.fail') allows an unprivileged user to corrupt arbitrary file page-cache pages using the AF_ALG crypto interface and the splice() system call. In Talos Linux, this can be exploited by a standard Kubernetes pod to poison binaries (such as /usr/sbin/nft) in containerd snapshot layers shared with privileged DaemonSets like kube-proxy. When the privileged service executes the corrupted binary, the attacker gains root-level code execution on the host. The issue is resolved in Talos v1.13.0 and v1.12.7 by updating to Linux kernel 6.18.25, which includes the necessary revert of in-place optimization in algif_aead.
Affected products
- Sidero Labs Talos Linux < 1.12.7, < 1.13.0
Timeline
- 2026-05-01: disclosed: Initial advisory publication by Sidero Labs
- 2026-05-07: advisory: GitHub Advisory published
- 2026-05-07: patched: Fixes available in Talos v1.12.7 and v1.13.0
References
- https://github.com/siderolabs/talos/security/advisories/GHSA-m38g-vww2-mvgx
- https://github.com/Percivalll/Copy-Fail-CVE-2026-31431-Kubernetes-PoC
- https://github.com/theori-io/copy-fail-CVE-2026-31431
- https://xint.io/blog/copy-fail-linux-distributions
- https://api.github.com/repos/siderolabs/talos/security-advisories/GHSA-m38g-vww2-mvgx