CVE-2026-34532: Parse Server: Cloud function validator bypass via prototype chain traversal

Severity: critical (CVSS 9.1 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.3% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-03-31 · updated 2026-07-24
Weakness: CWE-863

Description

Parse Server is an open source backend that can be deployed to any infrastructure that can run Node.js. Prior to versions 8.6.67 and 9.7.0-alpha.11, an attacker can bypass Cloud Function validator access controls by appending "prototype.constructor" to the function name in the URL. When a Cloud Function handler is declared using the function keyword and its validator is a plain object or arrow function, the trigger store traversal resolves the handler through its own prototype chain while the validator store fails to mirror this traversal, causing all access control enforcement to be skipped. This allows unauthenticated callers to invoke Cloud Functions that are meant to be protected by validators such as requireUser, requireMaster, or custom validation logic. This issue has been patched in versions 8.6.67 and 9.7.0-alpha.11.

Affected products

parse-community parse-server: before 8.6.67; from 9.0.0 before 9.7.0; 9.7.0-alpha1, 9.7.0-alpha10, 9.7.0-alpha2, 9.7.0-alpha3, 9.7.0-alpha4, 9.7.0-alpha5 (+4) — fixed in 8.6.67, 9.7.0

How to fix

Upgrade to a fixed version: parse-community parse-server 8.6.67, 9.7.0. Check the vendor advisory for mitigations.

References

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