Parse Server is an open‑source backend that can run on any Node.js infrastructure. Prior to the 9.6.0‑alpha.20 and 8.6.44 releases, a malicious request can exploit prototype pollution in the deep‑copy mechanism. By bypassing the default request keyword deny‑list protection, an attacker can inject disallowed fields into class schemas that are locked against field addition. The injected fields create permanent schema type conflicts that cannot be resolved even when using the master key. The underlying weakness is prototype pollution (CWE‑1321) and the impact is a corruption of database schema definitions, potentially causing application failures and a loss of data integrity.

Affected systems are deployments of the parse-community:parse-server component that run any version before 9.6.0‑alpha.20 or 8.6.44. The CPE listing indicates that all alpha releases up to alpha19 and the earlier 8.x releases are vulnerable. Versions 9.6.0‑alpha.20+, 8.6.44+, or later fixes are not affected.

The CVSS v3 score is 5.3, which represents moderate severity, while the EPSS score is less than 1 %, indicating a low likelihood of exploitation. The vulnerability is not listed in the CISA KEV catalog. It is inferred from the description that the attack vector is remote via a crafted HTTP request to the Parse Server API, as the prototype pollution is introduced through request processing. No known workarounds exist; the only remediation is upgrading to a fixed version.