GHSA-6hjj-gq77-j4qw Label Studio Object Relational Mapper Leak Vulnerability in Filtering Task
IntroductionThis write-up describes a vulnerability found in [Label Studio](https://github.com/HumanSignal/label-studio), a popular open source data labeling tool. The vulnerability affects all versions of Label Studio prior to `1.9.2post0` and was tested on version `1.8.2`.OverviewIn all current versions of [Label Studio](https://github.com/HumanSignal/label-studio), the application allows users to insecurely set filters for filtering tasks. An attacker can construct a *filter chain* to filter tasks based on sensitive fields for all user accounts on the platform by exploiting Django's Object Relational Mapper (ORM). Since the results of query can be manipulated by the ORM filter, an attacker can leak these sensitive fields character by character. For an example, the following filter chain will task results by the password hash of an account on Label Studio.For consistency, this type of vulnerability will be termed as **ORM Leak** in the rest of this disclosure.In addition, Label Studio had a hard coded secret key that an attacker can use to forge a session token of any user by exploiting this ORM Leak vulnerability to leak account password hashes.DescriptionThe following code snippet from the `ViewSetSerializer` in [`label_studio/data_manager/serializers.py`](https://github.com/HumanSignal/label-studio/blob/1.8.2/label_studio/data_manager/serializers.py#L115) insecurely creates `Filter` objects from a JSON `POST` request to the `/api/dm/views/{viewId}` API endpoint.These `Filter` objects are then applied in the `TaskQuerySet` in [`label_studio/data_manager/managers.py`](https://github.com/HumanSignal/label-studio/blob/1.8.2/label_studio/data_manager/managers.py#L473).User provided filters are insecurely applied here by calling the `apply_filters` that constructs the Django ORM filter.The `PreparedTaskManager` in [`label_studio/data_manager/managers.py`](https://github.com/HumanSignal/label-studio/blob/1.8.2/label_studio/data_manager/managers.py#L655) uses the vulnerable `TaskQuerySet` for building the Django queryset for querying `Task` objects, as shown in the following code snippet.Special Django method for the `models.Manager` class that is used to retrieve the queryset for querying objects of a model.Uses the vulnerable `TaskQuerySet` that was explained above.The following code snippet of the `Task` model in [`label_studio/tasks/models.py`](https://github.com/HumanSignal/label-studio/blob/1.8.2/label_studio/tasks/models.py#L49C1-L102C102) shows that the vulnerable `PreparedTaskManager` is set as a class variable, along with the `updated_by` relational mapping to a Django user that will be exploited as the entrypoint of the filter chain.The entry point of the filter chain to filter by the `updated_by__active_organization__active_users__password`.The vulnerable `PreparedTaskManager` being set that will be exploited.Finally, the `TaskListAPI` view set in [`label_studio/tasks/api.py`](https://github.com/HumanSignal/label-studio/blob/1.8.2/label_studio/tasks/api.py#L205) with the `/api/tasks` API endpoint uses the vulnerable `PreparedTaskManager` to filter `Task` objects.Uses the vulnerable `PreparedTaskManager` to filter objects.Proof of ConceptBelow are the steps to exploit about how to exploit this vulnerability to leak the password hash of an account on Label Studio.Create two accounts on Label Studio and choose one account to be the victim and the other the hacker account that you will use.Create a new project or use an existing project, then add a task to the project. Update the task with the hacker account to cause the entry point of the filter chain.Navigate to the task view for the project and add any filter with the `Network` inspect tab open on the browser. Look for a `PATCH` request to `/api/dm/views/{view_id}?interaction=filter&project={project_id}` and save the `view_id` and `project_id` for the next step.Download the attached proof of concept exploit script named `labelstudio_ormleak.py`. This script will leak the password hash of the victim account character by character. Run the following command to run the exploit script, replacing the `{view_id}`, `{project_id}`, `{cookie_str}` and `{url}` with the corresponding values. For further explanation run `python3 labelstudio_ormleak.py --help`.The following example GIF demonstrates exploiting this ORM Leak vulnerability to retrieve the password hash `pbkdf2_sha256$260000$KKeew1othBwMKk2QudmEgb$ALiopdBpWMwMDD628xeE1Ie7YSsKxdXdvWfo/PvVXvw=`.![labelstudio_ormleak_poc](https://user-images.githubusercontent.com/139727151/266986646-a3d1367c-fb4d-4482-9b6a-18a5d7316385.gif)ImpactThis vulnerability can be exploited to completely compromise the confidentiality of highly sensitive account information, such as account password hashes. For all versions `<=1.8.1`, this finding can also be chained with hard coded `SECRET_KEY` to forge session tokens of any user on Label Studio and could be abuse to deteriorate the integrity and availability.Remediation AdviceDo not use unsanitised values for constructing a filter for querying objects using Django's ORM. Django's ORM allows querying by relation field and performs auto lookups, that enable filtering by sensitive fields.Validate filter values to an allow list before performing any queries.DiscoveredAugust 2023, Alex Brown, elttam`labelstudio_ormleak.py` proof of concept
CVSS v3.1 score: 7.5