CVE-2026-107728

Strawberry GraphQL is a library for creating GraphQL APIs. From 0.217.0 until 0.326.1, PermissionExtension.resolve() on a synchronous field resolver evaluates the result of has_permission() for truthiness. When a custom permission declares has_permission() as a normal function but returns an awaitable, supports_sync does not classify it as asynchronous, the awaitable is not awaited, and its inherently truthy object value permits the protected resolver to run even when the result would resolve to false. This affects synchronous field resolvers under both execute_sync() and execute(); permissions declared with async def has_permission() and synchronous permissions returning a boolean are not affected. This issue is fixed in version 0.326.1.

Strawberry GraphQL is a library for creating GraphQL APIs. From 0.217.0 until 0.326.1, PermissionExtension.resolve() on a synchronous field resolver evaluates the result of has_permission() for truthiness. When a custom permission declares has_permission() as a normal function but returns an awaitable, supports_sync does not classify it as asynchronous, the awaitable is not awaited, and its inherently truthy object value permits the protected resolver to run even when the result would resolve to false. This affects synchronous field resolvers under both execute_sync() and execute(); permissions declared with async def has_permission() and synchronous permissions returning a boolean are not affected. This issue is fixed in version 0.326.1.

Summary

PermissionExtension.resolve() evaluates the return value of has_permission() for truthiness on the synchronous path. supports_sync only classifies a permission as asynchronous when has_permission is declared with async def (via inspect.iscoroutinefunction), so a plain def that returns an awaitable is treated as synchronous. An awaitable is always truthy, so the check passes even when it resolves to False and the protected resolver runs.

The resolve path is chosen by the field resolver, not by the execution method, so any field with a synchronous resolver is affected under both execute_sync() and execute(). Permissions declared with async def has_permission(), or a plain def returning a boolean, are not affected.

Details

The affected code is PermissionExtension.resolve() in strawberry/permission.py. A permission attached to a field whose has_permission is a normal def returning an awaitable reaches this path; the awaitable is never awaited and its truthiness grants access. resolve_async() is not affected because it uses await_maybe().

PoC

import strawberry
from strawberry.permission import BasePermission


class DenyViaAwaitable(BasePermission):
    message = "denied"

    def has_permission(self, source, info, **kwargs):
        async def result():
            return False

        return result()


@strawberry.type
class Query:
    @strawberry.field(permission_classes=[DenyViaAwaitable])
    def secret(self) -> str:
        return "secret"


schema = strawberry.Schema(Query)
print(schema.execute_sync("{ secret }").data)  # {'secret': 'secret'} instead of a permission error

Impact

An application using a custom permission whose has_permission is a normal def returning an awaitable can unintentionally grant access to the protected field. Standard permissions (a def returning a boolean, or an async def) are not affected, so exploitability depends on the application using this specific permission shape.

Fix

The synchronous path now fails closed: if has_permission() returns an awaitable, an error is raised instead of granting access.

Strawberry GraphQL is a library for creating GraphQL APIs. From 0.217.0 until 0.326.1, PermissionExtension.resolve() on a synchronous field resolver evaluates the result of has_permission() for truthiness. When a custom permission declares has_permission() as a normal function but returns an awaitable, supports_sync does not classify it as asynchronous, the awaitable is not awaited, and its inherently truthy object value permits the protected resolver to run even when the result would resolve to false. This affects synchronous field resolvers under both execute_sync() and execute(); permissions declared with async def has_permission() and synchronous permissions returning a boolean are not affected. This issue is fixed in version 0.326.1.

Strawberry GraphQL is a library for creating GraphQL APIs. From 0.217.0 until 0.326.1, PermissionExtension.resolve() on a synchronous field resolver evaluates the result of has_permission() for truthiness. When a custom permission declares has_permission() as a normal function but returns an awaitable, supports_sync does not classify it as asynchronous, the awaitable is not awaited, and its inherently truthy object value permits the protected resolver to run even when the result would resolve to false. This affects synchronous field resolvers under both execute_sync() and execute(); permissions declared with async def has_permission() and synchronous permissions returning a boolean are not affected. This issue is fixed in version 0.326.1.

Summary

PermissionExtension.resolve() evaluates the return value of has_permission() for truthiness on the synchronous path. supports_sync only classifies a permission as asynchronous when has_permission is declared with async def (via inspect.iscoroutinefunction), so a plain def that returns an awaitable is treated as synchronous. An awaitable is always truthy, so the check passes even when it resolves to False and the protected resolver runs.

The resolve path is chosen by the field resolver, not by the execution method, so any field with a synchronous resolver is affected under both execute_sync() and execute(). Permissions declared with async def has_permission(), or a plain def returning a boolean, are not affected.

Details

The affected code is PermissionExtension.resolve() in strawberry/permission.py. A permission attached to a field whose has_permission is a normal def returning an awaitable reaches this path; the awaitable is never awaited and its truthiness grants access. resolve_async() is not affected because it uses await_maybe().

PoC

import strawberry
from strawberry.permission import BasePermission


class DenyViaAwaitable(BasePermission):
    message = "denied"

    def has_permission(self, source, info, **kwargs):
        async def result():
            return False

        return result()


@strawberry.type
class Query:
    @strawberry.field(permission_classes=[DenyViaAwaitable])
    def secret(self) -> str:
        return "secret"


schema = strawberry.Schema(Query)
print(schema.execute_sync("{ secret }").data)  # {'secret': 'secret'} instead of a permission error

Impact

An application using a custom permission whose has_permission is a normal def returning an awaitable can unintentionally grant access to the protected field. Standard permissions (a def returning a boolean, or an async def) are not affected, so exploitability depends on the application using this specific permission shape.

Fix

The synchronous path now fails closed: if has_permission() returns an awaitable, an error is raised instead of granting access.

Summary

PermissionExtension.resolve() evaluates the return value of has_permission() for truthiness on the synchronous path. supports_sync only classifies a permission as asynchronous when has_permission is declared with async def (via inspect.iscoroutinefunction), so a plain def that returns an awaitable is treated as synchronous. An awaitable is always truthy, so the check passes even when it resolves to False and the protected resolver runs.

The resolve path is chosen by the field resolver, not by the execution method, so any field with a synchronous resolver is affected under both execute_sync() and execute(). Permissions declared with async def has_permission(), or a plain def returning a boolean, are not affected.

Details

The affected code is PermissionExtension.resolve() in strawberry/permission.py. A permission attached to a field whose has_permission is a normal def returning an awaitable reaches this path; the awaitable is never awaited and its truthiness grants access. resolve_async() is not affected because it uses await_maybe().

PoC

import strawberry
from strawberry.permission import BasePermission


class DenyViaAwaitable(BasePermission):
    message = "denied"

    def has_permission(self, source, info, **kwargs):
        async def result():
            return False

        return result()


@strawberry.type
class Query:
    @strawberry.field(permission_classes=[DenyViaAwaitable])
    def secret(self) -> str:
        return "secret"


schema = strawberry.Schema(Query)
print(schema.execute_sync("{ secret }").data)  # {'secret': 'secret'} instead of a permission error

Impact

An application using a custom permission whose has_permission is a normal def returning an awaitable can unintentionally grant access to the protected field. Standard permissions (a def returning a boolean, or an async def) are not affected, so exploitability depends on the application using this specific permission shape.

Fix

The synchronous path now fails closed: if has_permission() returns an awaitable, an error is raised instead of granting access.

Root has patched CVE-2026-107728 in the strawberry-graphql package for Root:PyPI. Multiple fixed versions available.