Hot Chocolate is an open-source GraphQL server. Prior to versions 12.22.7, 13.9.16, 14.3.1, and 15.1.14, Hot Chocolate's recursive descent parser `Utf8GraphQLParser` has no recursion depth limit. A crafted GraphQL document with deeply nested selection sets, object values, list values, or list types can trigger a `StackOverflowException` on payloads as small as 40 KB. Because `StackOverflowException` is uncatchable in .NET (since .NET 2.0), the entire worker process is terminated immediately. All in-flight HTTP requests, background `IHostedService` tasks, and open WebSocket subscriptions on that worker are dropped. The orchestrator (Kubernetes, IIS, etc.) must restart the process. This occurs before any validation rules run — `MaxExecutionDepth`, complexity analyzers, persisted query allow-lists, and custom `IDocumentValidatorRule` implementations cannot intercept the crash because `Utf8GraphQLParser.Parse` is invoked before validation. The `MaxAllowedFields=2048` limit does not help because the crashing payloads contain very few fields. The fix in versions 12.22.7, 13.9.16, 14.3.1, and 15.1.14 adds a `MaxAllowedRecursionDepth` option to `ParserOptions` with a safe default, and enforces it across all recursive parser methods (`ParseSelectionSet`, `ParseValueLiteral`, `ParseObject`, `ParseList`, `ParseTypeReference`, etc.). When the limit is exceeded, a catchable `SyntaxException` is thrown instead of overflowing the stack. There is no application-level workaround. `StackOverflowException` cannot be caught in .NET. The only mitigation is to upgrade to a patched version. Operators can reduce (but not eliminate) risk by limiting HTTP request body size at the reverse proxy or load balancer layer, though the smallest crashing payload (40 KB) is well below most default body size limits and is highly compressible (~few hundred bytes via gzip).
An attacker sends a specially crafted GraphQL document containing deeply nested selection sets, object values, list values, or list types. The `Utf8GraphQLParser` processes such a structure recursively without any depth limit, leading to call stack exhaustion and triggering `StackOverflowException`. Since this exception cannot be caught in .NET (from version 2.0 onwards), the entire worker process is immediately terminated and all active HTTP requests, `IHostedService` tasks, and WebSocket subscriptions are abandoned. The attack occurs before any validation rules are executed (e.g., `MaxExecutionDepth`, complexity analyzers, query allow-lists), as parsing happens before validation.
An attacker can completely and repeatedly stop the application server worker process (DoS), causing service unavailability and forcing orchestrator restarts (e.g., Kubernetes, IIS). All in-flight requests and active WebSocket connections are interrupted with each attack.
Hot Chocolate must be immediately updated to version 12.22.7, 13.9.16, 14.3.1, or 15.1.14, which introduce the `MaxAllowedRecursionDepth` option in `ParserOptions` with a secure default value. There is no effective workaround at the application level — restricting request body size at the reverse proxy or load balancer level reduces risk but does not eliminate it, as the minimal crash-inducing payload (~40 KB) is well below most default limits and is highly compressible.
Hot Chocolate (open-source GraphQL server) in versions prior to 12.22.7, 13.9.16, 14.3.1, and 15.1.14.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H