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HIGH severity

CVE-2021-39187 — parse-server

HIGHFix: parse-community/parse-server@308668c

CVE-2021-39187 is a high-severity (CVSS 7.5) CWE-74 vulnerability in parse-server. A fix is available for parse-server — see the affected versions and patch details below.

Parse Server crashes with query parameter

Also known asBIT-parse-2021-39187GHSA-xqp8-w826-hh6x
Published
Updated
Affected
1 pkg
Patched
1 / 1
Exploits
None indexed
Exploitation data as of Oct 10, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

EPSS Exploitation Probability

via FIRST.org ↗
1.8%probability of exploitation in next 30 days
Lower Risk0.00%
Lower risk than most CVEs78th percentile — riskier than 78% of all scored CVEsHighest risk
0.16%0.88%1.60%2.32%0.7%1.8%Apr 26Aug 26Oct 26

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

CVE-2021-39187 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.

Where this sits among everything scored

Of 385,738 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.

Real-World Exposure

1 pkg affected

How broadly this vulnerability is actually deployed: weekly install volume shows current usage, and reverse-dependency count shows how many other packages break if it stays unpatched.

62other npm packages depend on this — each one inherits the vulnerability until it's patched upstream
parse-servernpm
44Kdownloads / week

Description

Parse Server is an open source backend that can be deployed to any infrastructure that can run Node.js. Prior to version 4.10.3, Parse Server crashes when if a query request contains an invalid value for the explain option. This is due to a bug in the MongoDB Node.js driver which throws an exception that Parse Server cannot catch. There is a patch for this issue in version 4.10.3. No workarounds aside from upgrading are known to exist.

Affected Packages

1 total 1 fixed
EcosystemPackageVulnerable rangeFix
📦npmparse-serverall versions4.10.3npm install parse-server@4.10.3

Affected Products

1 product · 1 configurations
Application
parse-serverparseplatform
< 4.10.3
range

Detection & mitigation playbook

Open-source dependency

  1. Detect

    Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for parse-server, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

  2. Fix

    Update parse-server to 4.10.3 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-39187 is resolved across your whole dependency graph.

  3. Workarounds

    If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

Frequently Asked Questions

Parse Server is an open source backend that can be deployed to any infrastructure that can run Node.js. Prior to version 4.10.3, Parse Server crashes when if a query request contains an invalid value for the `explain` option. This is due to a bug in the MongoDB Node.js driver which throws an exception that Parse Server cannot catch. There is a patch for this issue in version 4.10.3. No workarounds aside from upgrading are known to exist.
O3 Security · Impact-Aware SCA

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CVE-2021-39187: parse-server — Fixed in 4.10.3