CVE-2026-33421: Parse Server: LiveQuery bypasses CLP pointer permission enforcement
Impact
Parse Server's LiveQuery WebSocket interface does not enforce Class-Level Permission (CLP) pointer permissions (readUserFields and pointerFields). Any authenticated user can subscribe to LiveQuery events and receive real-time updates for all objects in classes protected by pointer permissions, regardless of whether the pointer fields on those objects point to the subscribing user. This bypasses the intended read access control, allowing unauthorized access to potentially sensitive data that is correctly restricted via the REST API.
Patches
The LiveQuery server now enforces pointer permissions on each event. After the existing check passes (which defers pointer permissions by design), the fix checks whether any configured pointer field on the object points to the subscribing user. Events for objects that don't match are silently skipped, consistent with how ACL mismatches are handled.
Workarounds
Use ACLs on individual objects to restrict read access instead of relying solely on CLP pointer permissions. ACLs are enforced by LiveQuery.
Other sources
Parse Server is an open source backend that can be deployed to any infrastructure that can run Node.js. Prior to versions 8.6.53 and 9.6.0-alpha.42, Parse Server's LiveQuery WebSocket interface does not enforce Class-Level Permission (CLP) pointer permissions (readUserFields and pointerFields). Any authenticated user can subscribe to LiveQuery events and receive real-time updates for all objects in classes protected by pointer permissions, regardless of whether the pointer fields on those objects point to the subscribing user. This bypasses the intended read access control, allowing unauthorized access to potentially sensitive data that is correctly restricted via the REST API. This issue has been patched in versions 8.6.53 and 9.6.0-alpha.42.
— MITRE
Affected Software
Remediation
Event History
Frequently Asked Questions
What is the severity of CVE-2026-33421?
The severity of CVE-2026-33421 is classified as high due to the potential for unauthorized data access.
How do I fix CVE-2026-33421?
To fix CVE-2026-33421, upgrade to Parse Server version 9.6.0 or later, ensuring that Class-Level Permissions are correctly enforced.
Who is affected by CVE-2026-33421?
CVE-2026-33421 affects users of Parse Server versions prior to 9.6.0 and 8.6.53.
What can an attacker do with CVE-2026-33421?
An attacker can exploit CVE-2026-33421 to bypass Class-Level Permission checks and gain unauthorized access to user fields and pointer fields.
Is there a workaround for CVE-2026-33421?
Currently, there are no effective workarounds for CVE-2026-33421; upgrading to a patched version is recommended.