CVE-2021-39138Network attack vector

Access-control bypass via mislabeled anonymous sessions

Published Aug 18, 2021 · Updated Aug 4, 2024

Improper authentication in Parse Server before 4.5.1 allows remote attackers to obtain anonymous sessions mislabeled as password-authenticated. RestWrite.createSessionToken fails to copy the anonymous provider from authData, so createdWith.authProvider defaults to password instead of anonymous. Exploitation requires anonymous login and application logic that directly trusts createdWith; Parse Server itself does not use the field for authorization.

CVSS severity4.8
Medium
EPSS probability0.99%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper authentication in Parse Server before 4.5.1 allows remote attackers to obtain anonymous sessions mislabeled as password-authenticated. RestWrite.createSessionToken fails to copy the anonymous provider from authData, so createdWith.authProvider defaults to password instead of anonymous. Exploitation requires anonymous login and application logic that directly trusts createdWith; Parse Server itself does not use the field for authorization.

The record

CVE
CVE-2021-39138
Published
Aug 18, 2021
Updated
Aug 4, 2024
Vendor
Parse Platform
Product
Parse Server
Classifications
CWE-863, CWE-287, T1078
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Aug 18, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 4, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=< 4.5.1

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Parse Platform · Parse Serverversion=< 4.5.1

Published CVSS scores

6.5NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N
4.8GitHub, Inc.CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N
6.4NIST NVDAV:N/AC:L/Au:N/C:P/I:P/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-863Incorrect Authorization
CWE-287Improper Authentication
T1078Valid Accounts

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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