CVE-2026-95838: containerd: Unpack DoS via repeated opaque whiteouts

A vulnerability exists in containerd’s layer unpack handler where the processing of certain image layers causes superlinear time complexity. During the unpack operation, specific file configurations within the layer can trigger repeated directory traversals.

Consequently, pulling or importing a maliciously crafted image can result in increased unpack times and a moderate increase in CPU usage. This delays container startup, even if the compressed image layers are small. Additionally, in orchestrators like Kubernetes that apply concurrency limits to image pulls, these excessively long operations can reduce the available concurrency for other pulls, potentially delaying unrelated container deployments.