A race condition during docker cp mount setup allows a malicious container to create empty files or directories at arbitrary absolute paths on the host filesystem.
This advisory covers the race during mountpoint creation. The related race during the subsequent mount syscall is tracked in GHSA-rg2x-37c3-w2rh
When copying files into a container, the daemon sets up a temporary filesystem view by bind-mounting volumes into a private mount namespace. During this setup, the mount destination path is first resolved within the container's root filesystem using GetResourcePath, and then used to create the mountpoint (file or directory) if it does not already exist via createIfNotExists.
Between path resolution and mountpoint creation, a process running inside the container can swap a path component for a symlink pointing to an arbitrary location on the host. Because createIfNotExists operates on the already-resolved absolute path using standard os.MkdirAll and os.OpenFile — which follow symlinks in intermediate path components — the symlink is followed and the file or directory is created outside the container root filesystem, as root.
A malicious container can create empty files or directories at arbitrary absolute paths on the host filesystem, running as root. This enables persistent denial of service — for example:
/etc/docker/daemon.json into a directory prevents the daemon from restarting/etc/nologin prevents user loginsThe container does not gain read or write access to existing host files — only the ability to create new empty files or directories at chosen paths.
docker cp into that container, or call the PUT /containers/{id}/archive or HEAD /containers/{id}/archive API endpoints.Mountpoint creation is now scoped to the container root using os.Root (Go 1.24+), which refuses to follow symlinks that escape the opened root directory. All filesystem operations in createIfNotExists (MkdirAll, OpenFile) are performed through the os.Root handle, so even if a symlink swap occurs after path resolution, the creation stays confined to the container root.
docker cp with untrusted running containers.PUT /containers/{id}/archive, HEAD /containers/{id}/archive).| Software | From | Fixed in |
|---|---|---|
github.com/docker/docker
|
- | 28.5.2.x |
github.com/moby/moby/v2
|
- | 2.0.0-beta.14 |
github.com/moby/moby
|
- | 28.5.2.x |
A security vulnerability is a weakness in software, hardware, or configuration that can be exploited to compromise confidentiality, integrity, or availability. Many vulnerabilities are tracked as CVEs (Common Vulnerabilities and Exposures), which provide a standardized identifier so teams can coordinate patching, mitigation, and risk assessment across tools and vendors.
CVSS (Common Vulnerability Scoring System) estimates technical severity, but it doesn't automatically equal business risk. Prioritize using context like internet exposure, affected asset criticality, known exploitation (proof-of-concept or in-the-wild), and whether compensating controls exist. A "Medium" CVSS on an exposed, production system can be more urgent than a "Critical" on an isolated, non-production host.
A vulnerability is the underlying weakness. An exploit is the method or code used to take advantage of it. A zero-day is a vulnerability that is unknown to the vendor or has no publicly available fix when attackers begin using it. In practice, risk increases sharply when exploitation becomes reliable or widespread.
Recurring findings usually come from incomplete Asset Discovery, inconsistent patch management, inherited images, and configuration drift. In modern environments, you also need to watch the software supply chain: dependencies, containers, build pipelines, and third-party services can reintroduce the same weakness even after you patch a single host. Unknown or unmanaged assets (often called Shadow IT) are a common reason the same issues resurface.
Use a simple, repeatable triage model: focus first on externally exposed assets, high-value systems (identity, VPN, email, production), vulnerabilities with known exploits, and issues that enable remote code execution or privilege escalation. Then enforce patch SLAs and track progress using consistent metrics so remediation is steady, not reactive.
SynScan combines attack surface monitoring and continuous security auditing to keep your inventory current, flag high-impact vulnerabilities early, and help you turn raw findings into a practical remediation plan.