Security readout for executives and security teams
Plain-English summary
This issue can make MongoDB client-side field level encryption ineffective in narrow conditions. A vulnerable Java driver may fail to properly verify the KMS server certificate name, allowing a privileged network attacker to intercept KMS traffic. Systems not using Field Level Encryption are not affected.
Executive priority
Treat this as a targeted remediation for sensitive MongoDB Java applications using CSFLE. It is not broadly exploitable, but it can undermine encryption controls if an attacker controls the network path to KMS. Prioritize regulated or high-value data workloads first.
Technical view
CVE-2021-20328 is CWE-295 in MongoDB Java driver CSFLE support. Specific Java driver packages and versions fail correct hostname verification on KMS certificates. Combined with active MITM from a privileged network position, confidentiality and integrity of field-level encryption can be compromised. Java async, Scala, and reactive streams drivers are not impacted.
Likely exposure
Exposure is likely limited to applications using affected MongoDB Java driver versions with CSFLE enabled. Workloads without Field Level Encryption are not impacted. The source also states applications inside AWS, GCP, and Azure network fabrics using CSFLE-supported key services are not impacted due to compensating controls.
Exploitation context
The public bundle does not show active exploitation, and the CVE is not marked KEV. Exploitation requires an active man-in-the-middle position with privileged network access and user interaction per CVSS. This is serious where encryption protects sensitive fields across less-controlled network paths.
Researcher notes
The source bundle names MongoDB Java driver CSFLE hostname verification against KMS certificates and excludes Java async, Scala, and reactive streams drivers. Evidence does not include a patch version, public exploit, or KEV listing, so remediation should track MongoDB advisory guidance rather than assumed fixes.
Mitigation direction
- Identify Java applications using MongoDB CSFLE and affected driver packages.
- Check MongoDB JAVA-4017 and vendor guidance for fixed driver versions or workarounds.
- Prioritize remediation for CSFLE workloads outside protected cloud network fabrics.
- Avoid routing KMS traffic through untrusted or weakly controlled network paths.
- Confirm async, Scala, or reactive streams drivers before excluding systems.
Validation and detection
- Inventory MongoDB Java driver package names and versions in application dependencies.
- Confirm whether each application enables client-side field level encryption.
- Map KMS provider traffic paths and hosting environment for each affected application.
- Verify whether workloads run inside AWS, GCP, or Azure network fabrics.
- Review TLS/KMS connection validation findings against MongoDB advisory details.
Public sources used
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
Conservative CVE-to-ATT&CK context
These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.
ATT&CK lookup starting points
Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.
CWE-295: Exact CWE lookup
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Open ATT&CK lookupCVE-2021-20328 mapping review
Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.
Open ATT&CK lookup- Severity
- Medium
- CVSS
- 6.4 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:A/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:N
CNA and ADP enrichment extracted from CVE v5
These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.
CVSS vector scores
1 official scoreWe collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.
CVSS:3.1/AV:A/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:N1.25.2Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
6.4MediumVector: CVSS:3.1/AV:A/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:N
Source materials
- CVE List V5 sourceCVE List V5
- https://jira.mongodb.org/browse/JAVA-4017CVE reference · x_refsource_MISC
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.
Improper Certificate Validation
Improper Certificate Validation represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.