CVE-2021-39138
New anonymous user session acts as if it's created with password
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.
Attack profile
How easy it is to exploit
- Attack vector
- Network
- Complexity
- High
- Privileges needed
- None
- User interaction
- None
What an attacker can affect
- Confidentiality
- Low
- Integrity
- Low
- Availability
- None
Exploit likelihood
What each source reports
CVE List Score used
New anonymous user session acts as if it's created with password
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.
- Record
CVE-2021-39138- CVSS 3.1
- 4.8 Medium
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N - Weakness
- CWE-287
- Updated
- 2026-11-02
EUVDEUVD-2021-1504
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.
- Record
EUVD-2021-1504- CVSS 3.1
- 4.8 Medium
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N - Updated
- 2026-11-03
GitHub AdvisoriesGHSA-23r4-5mxp-c7g5
parse-server new anonymous user session acts as if it's created with password
Impact
Developers that use the REST API to signup users and also allow users to login anonymously. 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 currently doesn't use createdWith to make decisions on how things work internally, so if a developer isn't using createdWith directly, there's nothing to worry about. The vulnerability only affects users who depend on createdWith by using it directly.
Patches
Upgrade to version 4.5.1.
Workarounds
Don't use the createdWith Session field to make decisions if you allow anonymous login.
References
n/a
- Record
GHSA-23r4-5mxp-c7g5- CVSS 3.1
- 4.8 Medium
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N - Weakness
- CWE-287, CWE-863
- Updated
- 2026-11-02
NVD
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.
- Record
CVE-2021-39138- CVSS 3.1
- 4.8 Medium
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N - CVSS 3.1
- 6.5 Medium
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N - CVSS 2.0
- 6.4 Medium
AV:N/AC:L/Au:N/C:P/I:P/A:N - Weakness
- CWE-287, CWE-863
- Updated
- 2026-11-02
OSV
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.
- Record
CVE-2021-39138- CVSS 3.1
- 6.5 Medium
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N - Updated
- 2026-11-02
OSVGHSA-23r4-5mxp-c7g5
parse-server new anonymous user session acts as if it's created with password
Impact
Developers that use the REST API to signup users and also allow users to login anonymously. 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 currently doesn't use createdWith to make decisions on how things work internally, so if a developer isn't using createdWith directly, there's nothing to worry about. The vulnerability only affects users who depend on createdWith by using it directly.
Patches
Upgrade to version 4.5.1.
Workarounds
Don't use the createdWith Session field to make decisions if you allow anonymous login.
References
n/a
- Record
GHSA-23r4-5mxp-c7g5- CVSS 3.1
- 4.8 Medium
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N - Weakness
- CWE-287, CWE-863
- Updated
- 2026-11-02
OSVBIT-parse-2021-39138 No score
New anonymous user session acts as if it's created with password
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.
- Record
BIT-parse-2021-39138- Updated
- 2026-11-02
Affected products
Affected packages
| Package | Affected | Fixed |
|---|---|---|
parse-servernpm |
before 4.5.2 | 4.5.2 |
parseBitnami |
before 4.5.1 | 4.5.1 |
History
| Recorded | Changed | Sources |
|---|---|---|
| aliases | EUVD | |
| first indexed | CVE List, GitHub Advisories, NVD, OSV |
Dates are when Every CVE recorded each change. Upstream dates may differ.
In short
CVE-2021-39138 is a medium vulnerability (CVSS 4.8) in Parse-community Parse-server, published August 18, 2021. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.99%, the 62nd percentile. Fixed in parse-server 4.5.2.
References
github.com/parse-community/parse-server/security/advisories/GHSA-23r4-5mxp-c7g5
nvd.nist.gov/vuln/detail/CVE-2021-39138