GHSA-rrmm-9v76-h3p4: Portainer missing authorization on Docker plugin endpoints, which allows host RCE
SummaryPortainer enforces Role-Based Access Control (RBAC) on top of the Docker API. The proxy layer routes incoming Docker API requests to per-resource handlers (containers, images, services, volumes, etc.) that apply authorization checks.The Docker plugin management endpoints (`/plugins/*`) were not registered with a handler, so standard users with endpoint access could call privileged plugin operations — including installing and enabling plugins — directly against the underlying Docker daemon.The vulnerability is exposed when a non-admin Portainer user (Standard User role, or any role granted endpoint-level access) has been given access to a Docker endpoint via Portainer RBAC. Administrators and users without Docker endpoint access are not affected.A regular user with access to a Docker endpoint can:Pull an arbitrary plugin from any registry via `POST /plugins/pull`.Grant it the privileges it requests, including `CAP_SYS_ADMIN` and host-path mounts.Enable the plugin via `POST /plugins/{name}/enable`, at which point Docker runs the plugin with root privileges on the host.Docker plugins execute as root on the host and can request arbitrary host capabilities and mounts. Enabling a crafted plugin gives the user access to the host filesystem and equivalent to root on the Docker host.Severity**Critical** — CVSS 9.4
`CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H`**CWE-862** — Missing AuthorizationAffected VersionsThe vulnerability exists in every Portainer release where the Docker API proxy uses the prefix-allowlist routing model — `/plugins` has never been in the allowlist, and the fall-through path has never applied authorization.Fixes are included in the next release of each supported branch:| Branch              | First vulnerable | Fixed in   |
|---------------------|------------------|------------|
| 2.33.x (LTS)        | 2.33.0           | **2.33.8** |
| 2.39.x (LTS)        | 2.39.0           | **2.39.2** |
| 2.40.x (STS)        | 2.40.0           | **2.41.0** |Portainer LTS branches receive fixes for 6 months plus a 3-month overlap after the next LTS ships. STS releases are supported only until the next STS ships — the 2.40.x STS line ends with the 2.41.0 release. All releases **prior to 2.33.0 are end-of-life** and will not receive a fix; users on EOL versions should upgrade to a supported LTS branch.WorkaroundsAdministrators who cannot immediately upgrade can reduce exposure by temporarily **revoking Docker endpoint access for non-admin users** via Portainer RBAC until the patched release is deployed. This eliminates the attack surface without disruption for administrators. This does not replace the fix.Affected Code`/plugins` is not in `prefixProxyFuncMap`, so requests to plugin endpoints fall through to `executeDockerRequest` and are forwarded to the Docker daemon without any Portainer-side authorization check.ImpactAn authenticated, non-admin Portainer user with access to any Docker-enabled endpoint can:Install and enable arbitrary Docker plugins from any registry.Execute plugin code with root privileges on the Docker host (including declaring `CAP_SYS_ADMIN` and host-path mounts).Read and modify files on the host filesystem from a restricted account, overriding the administrator's security policy.Timeline2026-03-16: Reported via GitHub Security Advisory by **ikkebr**.2026-04-20: Fix merged to `develop`, `release/2.39`, and `release/2.33`.2026-04-29: 2.41.0 released.2026-05-07: 2.39.2-LTS and 2.33.8-LTS released.Credit**ikkebr** — identified and reported the proxy allowlist bypass affecting the Docker plugin management endpoints.
CVSS v4.0: 9.4
CVSS v3.1: 8.8