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Fencer Vulns
medium 6.5

CVE-2021-20330 json

Specific replication command with malformed oplog entries can crash secondaries

published 2021-12-15 4 y ago modified 2026-09-08 2 mo ago also BIT-mongodb-2021-20330 , EUVD-2021-7750

cvss
6.5
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
1.1%
EPSS 1.1% chance of exploitation in 30 days, percentile 65%
public exploits
0
none known

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.

Patch / fix

  • bitnami mongodb 4.0.25, 4.2.14, 4.4.6
  • MongoDB Inc. MongoDB Server 4.0.27, 4.2.16, 4.4.9
  • mongodb mongodb 4.0.27, 4.2.18, 4.4.9

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

cisa ICSA-26-218-01 updated cvss 6.5

ABB Ability Zenon

  • ABB Ability Zenon /all IIoT services with MongoDB 4.2
    affected: mitigation

Facts from CISA's republication of the vendor's own advisory (CSAF); the linked advisory is the authoritative source. CISA notification · csaf

red hat product security vex CVE-2021-20330 updated cvss 6.5

mongodb: specific replication command with malformed oplog entries can crash secondaries

  • Red Hat Update Infrastructure 3 for Cloud Providers mongodb
    affected: no fix planned “Will not fix”

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
none
Automatable
no
Technical impact
partial
Assessed
2 y ago

Exploit prediction

1.08% chance of exploitation in the next 30 days, higher than 65% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 3.1 6.5 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
NVD 3.1 6.5 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
NVD 2.0 4.0 AV:N/AC:L/Au:S/C:N/I:N/A:P
OSV 3.1 6.5 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Affected packages

ecosystem package affected fixed in
bitnami mongodb
>=4.0.0, <4.0.25
>=4.2.0, <4.2.14
>=4.4.0, <4.4.6
4.0.25
4.2.14
4.4.6

Affected products

  • MongoDB Inc. MongoDB Server
  • mongodb mongodb

Classification

Weakness
  • CWE-20 Improper Input Validation
Technology feeds

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.