Executive brief
Parse Server is a backend-as-a-service platform that manages database schemas and access control. An attacker with low-level privileges can exploit a prototype pollution flaw in the request processing pipeline to bypass schema protections and inject unauthorized fields into locked-down class schemas, causing permanent data structure conflicts that administrators cannot resolve even with master access.
Technical details
The vulnerability is a prototype pollution flaw in Parse Server's request processing logic. Parse Server performs a deep copy of incoming requests, which inadvertently strips __proto__ properties during cloning; the security-critical keyword denylist check runs after this step, so it never sees the poisoned prototype chain that an attacker can inject. This allows a low-privileged, authenticated attacker to craft a request with prototype pollution payloads that bypass both the default denylist protection and class-level field-addition permissions. The root cause is the order of operations: the cloning mechanism alters the data shape before security validation, creating a logic flaw in the security pipeline. The fix replaces the vulnerable third-party deep copy library with a built-in deep clone mechanism that safely handles prototype properties, allowing the denylist check to correctly reject prohibited keywords. Patches are available: version 8.6.44 and 9.6.0-alpha.20 or later.
Affected products
- Parse Community Parse Server 0 to 8.6.43; 9.0.0 to 9.6.0-alpha.19
Timeline
- 2026-03-17: disclosed: GHSA-9ccr-fpp6-78qf published
- 2026-03-17: patched: Parse Server 8.6.44 and 9.6.0-alpha.20+ released