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The vulnerability, identified as CVE-2026-30854, resides in Parse Server’s GraphQL implementation. When the security setting `graphQLPublicIntrospection` is explicitly disabled to prevent public schema viewing, the server fails to fully enforce this restriction . The flaw lies in the inspection logic, which only performed a flat, shallow check on the root level of a GraphQL query. It did not recursively traverse the query structure to examine nested elements . An attacker can craft a query that places a sensitive `__type` introspection field inside an “inline fragment” (e.g., ... on Query { __type(name:"User") { name } }). Because this fragment is nested, the shallow security check overlooks it, allowing the query to execute and return type information about the API schema, such as details of the “User” object, despite introspection being supposedly disabled . The `__schema` introspection, which reveals the entire API blueprint, remains unaffected, but this `__type` bypass still provides valuable reconnaissance data to an unauthenticated attacker .
dailycve form:
Platform: Parse Server
Version: 9.3.1-alpha.3 to <9.5.0-alpha.10
Vulnerability: Introspection Bypass
Severity: Moderate
Date: Mar 7, 2026
Prediction: Mar 10, 2026
What Undercode Say:
Analytics:
This vulnerability is a logic flaw in access control (CWE-863) . The vulnerable code performed a non-recursive check, failing to validate nested `__type` fields within inline fragments. The fix implemented a recursive walk of all selection sets to detect `__type` at any depth . To determine if your Parse Server instance is vulnerable, you can test the GraphQL endpoint with a crafted query.
Example curl command to test for the vulnerability
Replace http://localhost:1337/graphql with your actual GraphQL endpoint
curl -X POST http://localhost:1337/graphql \
-H "Content-Type: application/json" \
-d '{"query": "query { ... on Query { __type(name:\"User\") { name } } }"}'
A vulnerable server will return details about the "User" type, even if public introspection is disabled.
A patched server will block this query or return an error.
How Exploit:
An unauthenticated attacker can send a specially crafted GraphQL query to the endpoint. The query uses an inline fragment to nest the `__type` introspection field, bypassing the shallow security check .
Example exploit payload
query {
... on Query {
__type(name: "User") {
name
fields {
name
type {
name
}
}
}
}
}
This query attempts to fetch the schema details for the "User" object.
Protection from this CVE:
- Immediate Patching: Update Parse Server to version `9.5.0-alpha.10` or later, which contains the fix with recursive security checks .
- Workaround: If an immediate upgrade is not possible, enforce master key authentication for the GraphQL endpoint at the network layer (e.g., using a reverse proxy) to block all unauthenticated access .
Impact:
Successful exploitation allows an unauthenticated attacker to perform type reconnaissance. By leaking the structure of objects like “User,” the attacker can gain valuable insights into the data model, field names, and relationships. This information significantly expands the attack surface and can be used to craft more precise and damaging follow-on attacks .
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Sources:
Reported By: github.com
Extra Source Hub:
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