Ce mail provient de l'extérieur, restons vigilants ===================================================================== CERT-Renater Note d'Information No. 2026/VULN532 _____________________________________________________________________ DATE : 21/05/2026 HARDWARE PLATFORM(S): / OPERATING SYSTEM(S): Systems running Docker Engine versions prior to 29.5.1, docker/daemon (Go) versions up to and including 28.5.2, moby/v2/daemon (Go) versions prior to v2.0.0-beta.14. ===================================================================== https://github.com/moby/moby/security/advisories/GHSA-rg2x-37c3-w2rh https://github.com/moby/moby/security/advisories/GHSA-x86f-5xw2-fm2r https://github.com/moby/moby/security/advisories/GHSA-vp62-88p7-qqf5 _____________________________________________________________________ Race condition in docker cp allows bind mount redirection to host path High vvoland published GHSA-rg2x-37c3-w2rh May 18, 2026 Package Docker Engine Affected versions < 29.5.1 Patched versions 29.5.1 github.com/docker/docker/daemon (Go) Affected versions <= v28.5.2 None github.com/moby/moby/v2/daemon (Go) Patched versions < v2.0.0-beta.14 v2.0.0-beta.14 Description Summary A race condition during docker cp mount setup allows a malicious container to redirect a bind mount target to an arbitrary host path, potentially overwriting host files or causing denial of service. Details 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 is created inside the container root and then a bind mount is attached using the container-relative path resolved to an absolute host path. Between mountpoint creation and the mount() syscall, a process running inside the container can replace the destination (or a parent path component) with a symlink pointing to an arbitrary location on the host. The mount() syscall follows the symlink, causing the volume to be bind-mounted onto an arbitrary host path instead of the intended container path. Impact A malicious container can redirect a volume bind mount to an arbitrary host path. The impact depends on the volume content and mount options: If the volume is writable, arbitrary host files at the redirected path could be overwritten with the volume's contents. If the volume is read-only, the host path is masked by the mount for the duration of the operation, causing denial of service. In all cases the mount is temporary (torn down after the docker cp completes), but the effects of any writes persist. Conditions for exploitation A container must have at least one volume mount. A process inside the container must be able to rapidly create and swap symlinks at the volume mount destination path. An operator must initiate a docker cp into that container, or call the PUT /containers/{id}/archive or HEAD /containers/{id}/archive API endpoints. Not affected Containers that do not have volume mounts are not affected, as the race occurs during volume bind-mount setup. Workarounds Only run containers from trusted images. Avoid using docker cp with untrusted running containers. Use authorization plugins to restrict access to the archive API endpoints (PUT /containers/{id}/archive, HEAD /containers/{id}/archive). Severity High 7.2/ 10 CVSS v3 base metrics Attack vector Local Attack complexity High Privileges required Low User interaction Required Scope Changed Confidentiality None Integrity High Availability High CVSS:3.1/AV:L/AC:H/PR:L/UI:R/S:C/C:N/I:H/A:H CVE ID CVE-2026-42306 Weaknesses Weakness CWE-61 Weakness CWE-367 Credits @vvoland vvoland Remediation developer _____________________________________________________________________ `PUT /containers/{id}/archive` executes container binary on the host High vvoland published GHSA-x86f-5xw2-fm2r May 18, 2026 Package Docker Engine Affected versions < 29.5.1 Patched versions 29.5.1 github.com/docker/docker/daemon (Go) Affected versions <= v28.5.2 Patched versions none github.com/moby/moby/v2/daemon (Go) Affected versions < v2.0.0-beta.14 Patched versions v2.0.0-beta.14 Description Summary When a user uploads a compressed archive into a container, a malicious image can execute arbitrary code with daemon (host root) privileges. Details When handling PUT /containers/{id}/archive requests with compressed archives, the daemon decompresses them using external system binaries. Due to incorrect ordering of operations, these binaries are resolved from the container's filesystem rather than the host's. A container image that includes a trojanized decompression binary can achieve code execution as the daemon process whenever a compressed archive is uploaded to that container. The executed binary runs with the daemon's full privileges, including host root UID and unrestricted capabilities. Impact Arbitrary code execution as host root, crossing the container-to-host trust boundary. Conditions for exploitation A user must run a container from a malicious image that contains a trojanized decompression binary. The user must then upload a compressed archive (xz or gzip) into that container, either by piping a compressed archive via docker cp - or by calling the PUT /containers/{id}/archive API directly with compressed content. Not affected Standard docker cp usage is not affected, because the CLI sends uncompressed tar by default: docker cp ./file.txt mycontainer:/file.txt This can only be exploited when explicitly passing a xz or gzip-compressed archive to docker cp or the PUT /containers/{id}/archive API, for example: cat archive.tar.xz | docker cp - mycontainer:/dir Decompression formats using pure Go implementations (bzip2, zstd, and gzip when the container image does not contain an unpigz binary) are also not affected. Workarounds Only run containers from trusted images. Use authorization plugins to limit access to the PUT /containers/{id}/archive endpoint. Avoid piping compressed archives into containers created from untrusted images. Severity High 7.2/ 10 CVSS v3 base metrics Attack vector Local Attack complexity High Privileges required Low User interaction Required Scope Changed Confidentiality High Integrity High Availability None CVSS:3.1/AV:L/AC:H/PR:L/UI:R/S:C/C:H/I:H/A:N CVE ID CVE-2026-41567 Weaknesses No CWEs Credits @manizada manizada Reporter @vvoland vvoland Remediation developer _____________________________________________________________________ Race condition in docker cp allows creation of arbitrary empty files on the host via symlink swap Moderate vvoland published GHSA-vp62-88p7-qqf5 May 18, 2026 Package Docker Engine Affected versions < 29.5.1 Patched versions 29.5.1 github.com/docker/docker/daemon (Go) Affected versions <= v28.5.2 Patched versions None github.com/moby/moby/v2/daemon (Go) Affected versions < v2.0.0-beta.14 Patched versions v2.0.0-beta.14 Description Summary 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 Details 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. Impact 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: Converting /etc/docker/daemon.json into a directory prevents the daemon from restarting Creating /etc/nologin prevents user logins Overwriting critical system paths with empty files can break host services The 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. Conditions for exploitation A container must be running with a process that can rapidly create and swap symlinks at a volume mount destination path. An operator must initiate a docker cp into that container, or call the PUT /containers/{id}/archive or HEAD /containers/{id}/archive API endpoints. Not affected Containers that do not have volume mounts are not affected, as the race occurs during volume bind-mount setup. Patches 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. Workarounds Only run containers from trusted images. Avoid using docker cp with untrusted running containers. Use authorization plugins to restrict access to the archive API endpoints (PUT /containers/{id}/archive, HEAD /containers/{id}/archive). Severity Moderate 6.1/ 10 CVSS v3 base metrics Attack vector Local Attack complexity High Privileges required Low User interaction Required Scope Changed Confidentiality None Integrity Low Availability High CVSS:3.1/AV:L/AC:H/PR:L/UI:R/S:C/C:N/I:L/A:H CVE ID CVE-2026-41568 Weaknesses Weakness CWE-61 Weakness CWE-367 Credits @manizada manizada Reporter @vvoland vvoland Remediation developer ========================================================= + CERT-RENATER | tel : 01-53-94-20-44 + + 23/25 Rue Daviel | fax : 01-53-94-20-41 + + 75013 Paris | email:cert@support.renater.fr + =========================================================