CVE-2026-30854: Parse Server Information Disclosure Flaw

CVE-2026-30854 Overview

CVE-2026-30854 is an Authorization Bypass vulnerability affecting Parse Server, an open source backend framework designed to be deployed on any infrastructure that runs Node.js. The vulnerability exists in the GraphQL introspection control mechanism, where __type queries nested inside inline fragments can bypass the graphQLPublicIntrospection security setting.

When administrators configure graphQLPublicIntrospection to be disabled—a common security hardening measure to prevent schema reconnaissance—attackers can circumvent this control by crafting specially formatted GraphQL queries. By embedding __type queries within inline fragments (e.g., ... on Query { __type(name:"User") { name } }), unauthenticated users can extract type information from the GraphQL schema, enabling reconnaissance activities that the configuration was intended to prevent.

Critical Impact

Unauthenticated attackers can perform type reconnaissance on Parse Server GraphQL APIs even when introspection controls are explicitly disabled, potentially exposing sensitive schema information including custom types, field names, and data model structures.

Affected Products

• Parse Server versions 9.3.1-alpha.3 through 9.5.0-alpha.9
• parseplatform parse-server for Node.js
• Parse Server deployments with GraphQL API enabled

Discovery Timeline

• 2026-03-07 - CVE CVE-2026-30854 published to NVD
• 2026-03-10 - Last updated in NVD database

Technical Details for CVE-2026-30854

Vulnerability Analysis

This vulnerability is classified under CWE-863 (Incorrect Authorization), indicating a flaw in the access control logic that governs GraphQL introspection queries. The root issue lies in how Parse Server validates introspection requests when the graphQLPublicIntrospection configuration option is set to false.

The introspection control mechanism properly blocks direct __type and __schema queries at the top level of GraphQL operations. However, the validation logic fails to account for __type queries that are nested within GraphQL inline fragments. Inline fragments use the ... on TypeName { } syntax to conditionally include fields based on the returned type, and when combined with introspection meta-fields, they create a bypass path.

Notably, __schema introspection remains properly protected and is not affected by this bypass. The vulnerability specifically affects __type queries, which allow attackers to enumerate individual types by name and retrieve their field definitions, input types, and other metadata.

Root Cause

The root cause is an incomplete authorization check in the GraphQL query validation layer. When Parse Server processes incoming GraphQL queries, it inspects the operation for introspection-related fields to enforce the graphQLPublicIntrospection setting. However, the inspection does not recursively traverse inline fragment selections, allowing __type queries embedded within these fragments to escape detection.

This authorization gap enables queries structured with inline fragments targeting the Query type to include introspection calls that bypass the security control, while appearing as legitimate type-conditional selections.

Attack Vector

The attack is network-based and requires no authentication or user interaction. An attacker can craft malicious GraphQL queries targeting the Parse Server GraphQL endpoint, typically available at /graphql. By structuring the query with inline fragments, the attacker embeds __type introspection calls that reveal type definitions from the schema.

The attack enables reconnaissance activities including:

• Enumerating custom object types and their field structures
• Discovering input types and mutation parameters
• Mapping relationships between data models
• Identifying potentially sensitive fields and their types

This information can then be leveraged to craft targeted attacks against the application's data layer or identify additional attack surfaces within the API.

Detection Methods for CVE-2026-30854

Indicators of Compromise

• GraphQL queries containing inline fragments with __type introspection calls in server logs
• Unusual query patterns with ... on Query fragments combined with schema meta-fields
• Elevated GraphQL query volumes from unauthenticated sources
• Access log entries showing repeated requests to /graphql endpoints with varying type names in __type parameters

Detection Strategies

• Configure GraphQL query logging to capture full query bodies for analysis
• Implement Web Application Firewall (WAF) rules to detect inline fragments containing __type patterns
• Monitor for GraphQL queries that combine fragment syntax (...) with introspection fields (__type, name)
• Review application logs for type enumeration patterns indicating schema reconnaissance

Monitoring Recommendations

• Enable detailed GraphQL request logging including query content and client IP addresses
• Set up alerts for repeated __type queries from single IP addresses or sessions
• Monitor for sequential type name probing that suggests systematic enumeration
• Implement rate limiting on GraphQL endpoints to slow reconnaissance attempts

How to Mitigate CVE-2026-30854

Immediate Actions Required

• Upgrade Parse Server to version 9.5.0-alpha.10 or later immediately
• Audit GraphQL query logs for evidence of exploitation attempts
• Review any exposed type information for sensitive data disclosure
• Implement network-level access controls for GraphQL endpoints if public access is not required

Patch Information

The Parse Server maintainers have released a patch in version 9.5.0-alpha.10 that addresses this introspection bypass vulnerability. The fix ensures that __type queries nested within inline fragments are properly evaluated against the graphQLPublicIntrospection configuration setting.

For detailed patch information and security guidance, refer to the GitHub Security Advisory GHSA-q5q9-2rhp-33qw.

Workarounds

• Implement a reverse proxy or API gateway that inspects and blocks GraphQL queries containing __type within inline fragments
• Restrict access to the GraphQL endpoint using authentication requirements at the network or application layer
• Deploy a Web Application Firewall with custom rules to detect and block malicious introspection query patterns
• Temporarily disable GraphQL functionality if not required until the patch can be applied

# Example: Update Parse Server to patched version
npm install parse-server@9.5.0-alpha.10

# Verify the installed version
npm list parse-server