CVE-2021-39138

New anonymous user session acts as if it's created with password

MEDIUM
6.5
CVSS Score
Published: August 18, 2021 at 09:40 PM UTC
Updated: June 17, 2026 at 04:03 AM UTC
2 products affected across 2 vendorsParse ServerParse Server

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Severity
MEDIUM6.5
Exploit prediction
EPSS 1.0%

Description

Parse Server is an open source backend that can be deployed to any infrastructure that can run Node.js. Developers can use the REST API to signup users and also allow users to login anonymously. Prior to version 4.5.1, when an anonymous user is first signed up using REST, the server creates session incorrectly. Particularly, the `authProvider` field in `_Session` class under `createdWith` shows the user logged in creating a password. If a developer later depends on the `createdWith` field to provide a different level of access between a password user and anonymous user, the server incorrectly classified the session type as being created with a `password`. The server does not currently use `createdWith` to make decisions about internal functions, so if a developer is not using `createdWith` directly, they are not affected. The vulnerability only affects users who depend on `createdWith` by using it directly. The issue is patched in Parse Server version 4.5.1. As a workaround, do not use the `createdWith` Session field to make decisions if one allows anonymous login.

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

v < 4.5.1
Affected range stops below 4.5.1, so it looks safe — our inference, not a vendor statement
v < 4.5.1
Affected range stops below 4.5.1, so it looks safe — our inference, not a vendor statement

Remediation

No guide yet

No remediation guidance has been written for this CVE yet. What the record does show:

CVSS

Attack Vector
NETWORK
Complexity
LOW
Privileges
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality
LOW
Integrity
LOW
Availability
NONE
Vector?

Quick Info

StatusMODIFIED
CWE
CWE-287CWE-863

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