Specific replication command with malformed oplog entries can crash secondaries
Priority LOW 31CWE-20Published · Updated
Key facts
- Attack vector
- Network
- Privileges required
- Low
- User interaction
- None
- Attack complexity
- Low
- Impact type
- —
- Confidentiality · integrity · availability
- None · None · High
- Fix status
- Partial Red Hat: 1 without a fix
Attack profile from CVSS 3.1 · CNA. Fix status from CNA and Red Hat.
Summary
An attacker with basic CRUD permissions on a replicated collection can run the applyOps command with specially malformed oplog entries, resulting in a potential denial of service on secondaries. This issue affects MongoDB Server v4.0 versions prior to 4.0.27; MongoDB Server v4.2 versions prior to 4.2.16; MongoDB Server v4.4 versions prior to 4.4.9.
Why it matters now
Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.0108 65th percentileScored 2026-11-07
Fix Partial MongoDB Server (MongoDB Inc.): 4.0.27, 4.2.16, 4.4.9Red Hat: 1 without a fix
SSVC decision points
CISA ADP · SSVC 2.0.3
- Exploitation
- None
- Automatable
- No
- Technical impact
- Partial
The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.
Affected products
| Vendor | Product | Affected versions | Fixed in | Status | Source |
|---|---|---|---|---|---|
| MongoDB | MongoDB Server | 4.0 to before 4.0.27; 4.2 to before 4.2.16; 4.4 to before 4.4.9 | 4.0.27, 4.2.16, 4.4.9 | Patch available | CNA |
- MongoDB Server VendorMongoDB Affected 4.0 to before 4.0.27; 4.2 to before 4.2.16; 4.4 to before 4.4.9 Fixed in 4.0.27, 4.2.16, 4.4.9 Patch available CNA
CPE configurations NVD · 1
| CPE | Versions | Role | Vendor |
|---|---|---|---|
| cpe:2.3:a:mongodb:mongodb:*:*:*:*:*:*:*:* | 4.0.0 to before 4.0.25; 4.2.0 to before 4.2.14; 4.4.0 to before 4.4.6 | Vulnerable | MongoDB |
- cpe:2.3:a:mongodb:mongodb:*:*:*:*:*:*:*:* Versions 4.0.0 to before 4.0.25; 4.2.0 to before 4.2.14; 4.4.0 to before 4.4.6 Vulnerable ·MongoDB
Remediation
- Fix · CNA MongoDB Server (MongoDB Inc.) Fixed in 4.0.27, 4.2.16, 4.4.9
Vendor assessments
Red Hat
Red Hat rating: Moderate. Red Hat's page for this CVE →
| Product | Status | Plan or fix |
|---|---|---|
| Red Hat Update Infrastructure 3 for Cloud Providers | Affected | No fix planned: Will not fix |
Timeline
- 2026-10-02 Threatist record created from CVE-2021-20330
- 2026-10-03 Alias added: GHSA-8jvf-jqg4-r6h2
References
More Mongodb vulnerabilities
- TI-2025-13542 Zlib compressed protocol header length confusion may allow memory read KEVCVSS 4.0HIGH 8.7
- TI-2013-01669 MongoDB before 2.0.9 and 2.2.x before 2.2.4 does not properly validate requests to the… CVSS 2.0MEDIUM 6.0
- TI-2026-56639 Uncontrolled Resource Consumption in MongoDB Sharded Cluster Router Allows Unauthenticated Denial of Service CVSS 4.0HIGH 8.7
- TI-2026-56628 Reachable assertion in MongoDB Server CVSS 4.0HIGH 8.7
- TI-2026-15322 Improper Input Validation in MongoDB Aggregation Framework Allows Unauthenticated Denial of Service on mongos CVSS 4.0HIGH 8.7
- TI-2026-08537 Unbounded recursion in BSONColumn interleaved-reference causes pre-auth stack overflow CVSS 4.0HIGH 8.7
Sources
- CVE-2021-20330 · CVE Program
- CVE-2021-20330 · NVD
- FIRST EPSS
- GHSA-8jvf-jqg4-r6h2 · GitHub Advisory Database · CC BY 4.0
- CVE-2021-20330 · Red Hat security data · CC BY 4.0
This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences