CVE-2021-39187Public exploitNetwork attack vector

Unauthenticated server crash via invalid explain value

Published Sep 2, 2021 · Updated Aug 4, 2024

Denial of service in Parse Platform Parse Server before 4.10.3 allows remote attackers to crash the server via an invalid explain value. MongoStorageAdapter passes unsupported truthy explain values to the MongoDB Node.js driver, whose resulting exception escapes Parse Server error handling. A network query to a MongoDB-backed deployment requires no authentication or user interaction and terminates the service process.

CVSS severity7.5
High
EPSS probability1.82%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
Coverage for this vulnerability

See if you're affected

Explore vulnerability checks for your environment with Hinoki.

Book a demo

Summary

What happened

Denial of service in Parse Platform Parse Server before 4.10.3 allows remote attackers to crash the server via an invalid explain value. MongoStorageAdapter passes unsupported truthy explain values to the MongoDB Node.js driver, whose resulting exception escapes Parse Server error handling. A network query to a MongoDB-backed deployment requires no authentication or user interaction and terminates the service process.

The record

CVE
CVE-2021-39187
Published
Sep 2, 2021
Updated
Aug 4, 2024
Vendor
Parse Platform
Product
Parse Server
Classifications
CWE-755, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Sep 2, 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

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

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

  1. Affected versionversion=< 4.10.3

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Parse Platform · Parse Serverversion=< 4.10.3

Published CVSS scores

5.0NIST NVDAV:N/AC:L/Au:N/C:N/I:N/A:P
7.5GitHub, Inc.CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

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.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

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 exploitPublished

Weakness, pattern, technique

CWE-755Improper Handling of Exceptional Conditions
T1499.004Application or System Exploitation

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

See the directory against your own environment.

Your stack

Check the software in your environment

Book a demo to see how Hinoki identifies affected software and validates exploitability in your environment.

Book a demo