GHSA-x6xq-whh3-gg32

## Impact

Instances of the Apollo Router using either of the following may be impacted by a denial-of-service vulnerability.

1. External Coprocessing with specific configurations; or 2. Native Rust Plugins accessing the Router request body in the RouterService layer

Router customizations using Rhai scripts are **not** impacted.

### When using External Coprocessing:

Instances of the Apollo Router running versions >=1.21.0 and <1.52.1 are impacted by a denial-of-service vulnerability if **all** of the following are true:

1. Router has been configured to support External Coprocessing. 2. Router has been configured to send request bodies to coprocessors. This is a non-default configuration and must be configured intentionally by administrators.

You can identify if you are impacted by reviewing your router's configuration YAML for the following config:

```yaml ... coprocessor: url: http://localhost:9000 # likely different in your environment router: request: body: true # this must be set to 'true' to be impacted ... ``` External Coprocessing was initially made available as an experimental feature with [Router version 1.21.0](https://github.com/apollographql/router/releases/tag/v1.21.0) on 2023-06-20 and was made generally available with [Router version 1.38.0](https://github.com/apollographql/router/releases/tag/v1.38.0) on 2024-01-19. More information about the Router’s [External Coprocessing feature is available here](https://www.apollographql.com/docs/router/customizations/coprocessor).

### When using Native Rust Plugins:

Instances of the Apollo Router running versions >=1.7.0 and <1.52.1 are impacted by a denial-of-service vulnerability if **all** of the following are true:

1. Router has been configured to use a custom-developed Native Rust Plugin 2. The plugin accesses `Request.router_request` in the `RouterService` layer 3. You are accumulating the body from `Request.router_request` into memory

To use a plugin, you need to be running a customized Router binary. Additionally, you need to have a `plugins` section with at least one plugin defined in your Router’s configuration YAML. That plugin would also need to define a custom `router_service` method.

You can check for a defined plugin by reviewing for the following in your Router’s configuration YAML:

```yaml ... plugins: custom_plugin_name: # custom config here ... ```

You can check for a custom `router_service` method in a plugin, by reviewing for the following function signature in your plugin’s source:

```rust fn router_service(&self, service: router::BoxService) -> router::BoxService ```

More information about the Router’s [Native Rust Plugin feature is available here](https://www.apollographql.com/docs/router/customizations/native).

## Impact Detail

If using an impacted configuration, the Router will load entire HTTP request bodies into memory without respect to other HTTP request size-limiting configurations like `limits.http_max_request_bytes`. This can cause the Router to be out-of-memory (OOM) terminated if a sufficiently large request is sent to the Router.

By default, the Router sets `limits.http_max_request_bytes` to 2 MB. More information about the Router’s [request limiting features is available here](https://www.apollographql.com/docs/router/configuration/overview/#request-limits).

## Patches

[Apollo Router 1.52.1](https://github.com/apollographql/router/releases/tag/v1.52.1)

If you have an impacted configuration as defined above, please upgrade to at least Apollo Router 1.52.1.

## Workarounds If you cannot upgrade, you can mitigate the denial-of-service opportunity impacting External Coprocessors by setting the `coprocessor.router.request.body` configuration option to `false`. Please note that changing this configuration option will change the information sent to any coprocessors you have configured and may impact functionality implemented by those coprocessors.

If you have developed a Native Rust Plugin and cannot upgrade, you can update your plugin to either not accumulate the request body or enforce a maximum body size limit.

You can also mitigate this issue by limiting HTTP body payload sizes prior to the Router (e.g., in a proxy or web application firewall appliance).

## References [Apollo Router 1.52.1 Release Notes](https://github.com/apollographql/router/releases/tag/v1.52.1) [External Coprocessing documentation](https://www.apollographql.com/docs/router/customizations/coprocessor) [HTTP Request Limiting documentation](https://www.apollographql.com/docs/router/configuration/overview/#request-limits) [Native Rust Plugin documentation](https://www.apollographql.com/docs/router/customizations/native)