How severe is CVE-2021-20327?

CVE-2021-20327 has a CVSS 3.x base score of 6.4, rated medium severity. It is exploitable over an adjacent network with high attack complexity, requires no privileges and user interaction. Impact on confidentiality is high, integrity high, and availability none.

Is CVE-2021-20327 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (10th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-20327?

CVE-2021-20327 affects Mongodb Libmongocrypt. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2021-20327?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

When was CVE-2021-20327 published?

CVE-2021-20327 was published on 2021-02-25 and last updated on 2026-06-17.

CVE-2021-20327

CVE-2021-20327 is a medium-severity vulnerability in Mongodb Libmongocrypt with a CVSS 3.x base score of 6.4. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-295.

Key facts

Severity: Medium (CVSS 3.x base score 6.4)
CVSS v2: 4.3
EPSS exploit prediction: 0% (10th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-295
Affected product: Mongodb Libmongocrypt
Published: 2021-02-25
Last modified: 2026-06-17

Description

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

Frequently asked questions

What is CVE-2021-20327?: 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
How severe is CVE-2021-20327?: CVE-2021-20327 has a CVSS 3.x base score of 6.4, rated medium severity. It is exploitable over an adjacent network with high attack complexity, requires no privileges and user interaction. Impact on confidentiality is high, integrity high, and availability none.
Is CVE-2021-20327 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (10th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-20327?: CVE-2021-20327 affects Mongodb Libmongocrypt. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2021-20327?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
When was CVE-2021-20327 published?: CVE-2021-20327 was published on 2021-02-25 and last updated on 2026-06-17.

References

https://jira.mongodb.org/browse/NODE-3125

Affected products (1)

cpe:2.3:a:mongodb:libmongocrypt:1.2.0:*:*:*:*:node.js:*:*

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