Portainer has an endpoint security bypass via Swarm service create/update
Summary
Portainer enforces seven EndpointSecuritySettings restrictions that administrators configure to restrict the container configurations non-admin users can launch: privileged mode, host PID namespace, device mapping, capabilities, sysctls, security-opt (Seccomp / AppArmor), and bind mounts.
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 Swarm endpoint via Portainer RBAC. Admins and users without Swarm endpoint access are not affected.
These restrictions are enforced on the standard container creation path, but several of them are not applied on the Docker Swarm service API:
POST /services/create — 1 of 7 checks applied. CapabilityAdd, CapabilityDrop, Sysctls, and Privileges (Seccomp / AppArmor) are not parsed from the request body and are forwarded to the Docker daemon without validation.POST /services/{id}/update — 0 of 7 checks applied. The route dispatches to the generic restrictedResourceOperation, which validates RBAC ownership but does not inspect the request body or call fetchEndpointSecuritySettings().
The EndpointSecuritySettings checks apply when the administrator has configured any of AllowContainerCapabilitiesForRegularUsers, AllowSysctlSettingForRegularUsers, AllowSecurityOptForRegularUsers, or AllowBindMountsForRegularUsers to restrict standard users.
A regular user with access to a Docker Swarm endpoint can:
- Create a service with
CapabilityAdd: ["SYS_ADMIN", "NET_ADMIN", "SYS_PTRACE", …] or Privileges.Seccomp.Mode: "unconfined". - Create a benign service that passes ownership checks, then update it to add
CapabilityAdd: ["ALL"] plus a bind mount of /, scale to one replica, and access the host filesystem from the running container (e.g. via chroot /host).
In addition, the partial Mounts[] struct used by the bind-mount check inspects only the top-level Type field. A mount with Type: "volume" and VolumeOptions.DriverConfig.Options: {type: "none", o: "bind", device: "<host path>"} is forwarded to the Docker daemon unchanged; the local volume driver then materialises it as a bind-equivalent mount, bypassing AllowBindMountsForRegularUsers. The same field path is accepted by the standalone POST /volumes/create endpoint, which never had any AllowBindMountsForRegularUsers check on any branch.
This undermines the administrator's configured security policy on Swarm-enabled endpoints.
Affected Versions
The vulnerability exists in every Portainer release with Docker Swarm support — the service-creation path has never checked CapabilityAdd, CapabilityDrop, Sysctls, or Privileges, and the service-update path has never performed any EndpointSecuritySettings validation. The VolumeOptions.DriverConfig field has never been parsed by the partial service struct on any branch, so the volume-driver-bind variant (service create/update and direct /volumes/create) shares the same affected range.
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.
Workarounds
Administrators who cannot immediately upgrade can reduce exposure with the following measures. None of these replaces the fix.
- Temporarily revoke Swarm endpoint access for non-admin users via Portainer RBAC until the patched release is deployed. This eliminates the attack surface without service disruption for administrators.
- Segregate manager and worker nodes with placement constraints so user workloads do not run on manager nodes. This limits the exposure of the Swarm control plane if the bypass is exploited against a worker.
- Block creation of local-driver volumes that use
type: none / o: bind on untrusted endpoints via a daemon-side allowlist. This closes the volume-driver-bind variant until the patched release is deployed.
Affected Code
Service creation — only Mounts inspected (1/7)
```go
// api/http/proxy/factory/docker/services.go (pre-fix)
type PartialService struct {
TaskTemplate struct {
ContainerSpec struct {
Mounts []struct {
Type string
}
}
}
}
```
CapabilityAdd, CapabilityDrop, Sysctls, and `
