Rucio is a scientific data management framework. From 1.16.1 until 35.9.0, 38.6.0, and 41.0.0rc1, the /credentials/signurl endpoint reads X-Rucio-Account instead of the account stored in request.environ['issuer'] by token authentication. Any authenticated low-privilege user can supply root as the header value and pass the root-only get_signed_url permission check. The server then returns a presigned read, write, or delete URL for an attacker-selected object using stored S3, GCS, or Swift credentials, and X-Rucio-VO can select another tenant in multi-VO deployments. This permits data disclosure, modification, deletion, and cross-tenant access on cloud-backed RSEs. This issue is fixed in versions 35.9.0, 38.6.0, and 41.0.0rc1.

Affected: PyPI: rucio

## Summary The `/credentials/signurl` endpoint decides authorization from the client-supplied `X-Rucio-Account` HTTP header instead of the authenticated token's account. Any client holding **any** valid auth token (even a low-privilege account they legitimately own) can send `X-Rucio-Account: root` to pass the root-only permission check and have the Rucio server mint a presigned **read / write / delete** URL for an **arbitrary** object, signed with the RSE's stored S3 / GCS / Swift credentials.

## Details `SignURL.get()` takes the authorization principal from a request header and never uses the token-authenticated identity:

```python # lib/rucio/web/rest/flaskapi/v1/credentials.py account = request.headers.get('X-Rucio-Account', default=None) # L165 (attacker-controlled) ... result = get_signed_url(account, rse=rse, service=service, # L194 operation=operation, url=url, lifetime=lifetime, vo=vo) ```

The gateway then uses that header value as the `issuer` for the permission check:

```python # lib/rucio/gateway/credential.py auth_result = permission.has_permission(issuer=account, vo=vo, # L57 action='get_signed_url', kwargs=kwargs, ...) ```

and the permission function is root-only:

```python # lib/rucio/core/permission/generic.py def perm_get_signed_url(issuer, kwargs, session): return _is_root(issuer) # _is_root(x) -> x.external == 'root' ```

`InternalAccount('root', vo).external…