CVE-2026-33409

Description

### Impact An authentication bypass vulnerability allows an attacker to log in as any user who has linked a third-party authentication provider, without knowing the user's credentials. The attacker only needs to know the user's provider ID to gain full access to their account, including a valid session token. This affects Parse Server deployments where the server option `allowExpiredAuthDataToken` is set to `true`. The default value is `false`. ### Patches Auth providers are now always validated on login, regardless of the `allowExpiredAuthDataToken` setting. The option `allowExpiredAuthDataToken` has been deprecated and will be removed in a future major version. ### Workarounds Set `allowExpiredAuthDataToken` to `false` (the default) or remove the option from the server configuration.

How to fix CVE-2026-33409

To remediate CVE-2026-33409, upgrade the affected package to a fixed version below.

• —upgrade to 8.6.52 or later
• —upgrade to 9.6.0-alpha.41 or later

Is CVE-2026-33409 being exploited?

Low — EPSS is 0.0%, meaning exploitation activity has not been observed at scale.

Affected packages (2)

• from 0, < 8.6.52, >= 9.0.0, < 9.6.0
• >= 9.0.0, < 9.6.0-alpha.41

CVSS scores

References (7)

• ADVISORYnvd.nist.gov/vuln/detail/CVE-2026-33409
• PATCHgithub.com/parse-community/parse-server
• WEBgithub.com/parse-community/parse-server/commit/8d7df5639c4a35768fe8b78b4580b30e8a74721c
• WEBgithub.com/parse-community/parse-server/commit/98f4ba5bcf2c199bfe6225f672e8edcd08ba732d