dbcve.org
LibmongocryptApplication · MongoDB

CVE-2021-20327

MEDIUM · 6.8 CVSS v3.1 Published 2021-02-25
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
73/100
Remediation priority · Elevated
No privileges Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
A specific version of the Node.js mongodb-client-encryption module does not perform correct validation of the KMS server’s certificate. This vulnerability in combination with a privileged network position active MITM attack could result in interception of traffic between the Node.js driver and the KMS service rendering client-side field level encryption (CSFLE) ineffective. This issue was discovered during internal testing and affects mongodb-client-encryption module version 1.2.0, which was available from 2021-Jan-29 and deprecated in the NPM Registry on 2021-Feb-04. This vulnerability does not impact driver traffic payloads with CSFLE-supported key services from applications residing inside the AWS, GCP, and Azure nework fabrics due to compensating controls in these environments. This issue does not impact driver workloads that don’t use Field Level Encryption. This issue affect MongoDB Node.js Driver mongodb-client-encryption module version 1.2.0

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

The mongodb-client-encryption Node.js module version 1.2.0 fails to properly validate KMS server certificates, allowing a privileged network attacker performing MITM to intercept traffic between the MongoDB driver and the Key Management Service, defeating client-side field level encryption (CSFLE).

MitigationUpgrade mongodb-client-encryption to a version greater than 1.2.0 that implements proper certificate validation, or ensure workloads do not rely on CSFLE until the patch is applied.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
LibmongocryptApplication
Affected:= 1.2.0

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Adjacent
Complexity
High
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
None

CVSS:3.1/AV:A/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Identify installed version of mongodb-client-encryption
    Run 'npm list mongodb-client-encryption' or check package.json dependencies to find the exact installed version
    Affected if The installed version is exactly 1.2.0
  2. Check if CSFLE is in use
    Search codebase for 'ClientEncryption' class instantiation, 'encryptedFieldsMap', or 'autoEncryption' options in MongoClient configuration
    Affected if Application uses Client-Side Field Level Encryption with autoEncryption enabled
  3. Verify KMS provider configuration
    Inspect the CSFLE configuration for 'keyVaultNamespace' and any KMS provider settings (aws, azure, gcp, or kmip) that specify endpoint URLs
    Affected if Application connects to an external KMS endpoint for key management
  4. Check for custom TLS settings in KMS connection
    Search for tls, tlsAllowInvalidCertificates, tlsAllowInvalidHostnames, or similar options in the KMS provider configuration object
    Affected if TLS certificate validation options are absent or set to bypass validation (true or undefined defaults)
  5. Review network position for MITM exposure
    Assess whether the environment has network segments or proxies that could intercept traffic between the application and KMS endpoints
    Affected if Application communicates with KMS over networks where privileged attacker could perform MITM

A user is affected if mongodb-client-encryption version 1.2.0 is installed AND the application uses CSFLE with an external KMS provider that relies on the default (unvalidated) TLS connection.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

From vendor data
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Upgrade mongodb-client-encryption to a version greater than 1.2.0 that implements proper certificate validation, or ensure workloads do not rely on CSFLE until the patch is applied.

Fix this in Libmongocrypt Scoped from the published advisory
  • Consultation1.0 h
  • Implementation2.0 h
  • Testing2.0 h
  • Review / QA1.0 h
6.0 hours of engineering $1,040
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2021-20327 in production — separate from our analysis above.

No notes yet

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data