Executive brief
graphql-go is a GraphQL implementation for Go used to build GraphQL API servers. Versions through 0.8.1 fail to properly validate that variable values match their declared scalar types (String, ID, Boolean), allowing invalid inputs to be processed. In rare cases involving deeply nested values, this can trigger a stack overflow crash, causing temporary service unavailability.
Technical details
The vulnerability exists in the scalar type coercion functions (coerceString and coerceBool) in scalars.go, which do not validate input type against the declared scalar type as required by the GraphQL specification. An attacker can send a GraphQL request with scalar variables whose runtime type does not match the declared type; the library accepts these invalid values instead of raising a type error. In specific scenarios involving deeply nested structures, this type mismatch can lead to unbounded recursion and a fatal stack overflow, resulting in a denial-of-service. The attack requires the ability to send arbitrary GraphQL queries to the application; typical JSON-based web requests are unlikely to trigger the stack overflow condition.
Affected products
- graphql-go graphql through 0.8.1
Timeline
- 2026-08-25: disclosed