CVE-2021-20328
MEDIUMImproper Certificate Validation in MongoDB
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
Blast Radius
org.mongodb:mongodb-driver☕org.mongodb:mongodb-driver☕org.mongodb:mongodb-driver-sync☕org.mongodb:mongodb-driver-sync☕org.mongodb:mongodb-driver-sync☕org.mongodb:mongo-java-driver☕org.mongodb:mongo-java-driver☕org.mongodb:mongodb-driver-legacy+6 moreReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects Maven packages — download data is not available via public APIs for these ecosystems.
Description
Specific versions of the Java driver that support client-side field level encryption (CSFLE) fail to perform correct host name verification on 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 Java driver and the KMS service rendering Field Level Encryption ineffective. This issue was discovered during internal testing and affects all versions of the Java driver that support CSFLE. The Java async, Scala, and reactive streams drivers are not impacted. This vulnerability does not impact driver traffic payloads with CSFLE-supported key services originating from applications residing inside the AWS, GCP, and Azure network fabrics due to compensating controls in these environments. This issue does not impact driver workloads that don’t use Field Level Encryption.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| ☕Maven | org.mongodb:mongodb-driver | ≥ 3.11.0&&< 3.11.3 | 3.11.3 |
| ☕Maven | org.mongodb:mongodb-driver | ≥ 3.12.0&&< 3.12.8 | 3.12.8 |
| ☕Maven | org.mongodb:mongodb-driver-sync | ≥ 4.0.0&&< 4.0.6 | 4.0.6 |
| ☕Maven | org.mongodb:mongodb-driver-sync | ≥ 4.1.0&&< 4.1.2 | 4.1.2 |
| ☕Maven | org.mongodb:mongodb-driver-sync | ≥ 4.2.0&&< 4.2.1 | 4.2.1 |
| ☕Maven | org.mongodb:mongo-java-driver | ≥ 3.11.0&&< 3.11.3 | 3.11.3 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for org.mongodb:mongodb-driver. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update org.mongodb:mongodb-driver to 3.11.3 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-20328 is resolved across your whole dependency graph.
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.
How O3 protects you
O3 pinpoints whether CVE-2021-20328 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to CVE-2021-20328. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2021-20328 in your dependencies?
O3 detects CVE-2021-20328 across Maven dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.