How severe is CVE-2021-20330?

CVE-2021-20330 has a CVSS 3.x base score of 6.5, rated medium severity. It is exploitable over network with low attack complexity, requires low privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.

Is CVE-2021-20330 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (63rd percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-20330?

CVE-2021-20330 affects Mongodb. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2021-20330?

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

When was CVE-2021-20330 published?

CVE-2021-20330 was published on 2021-12-15 and last updated on 2026-06-17.

CVE-2021-20330

CVE-2021-20330 is a medium-severity vulnerability in Mongodb with a CVSS 3.x base score of 6.5. 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-20.

Key facts

Severity: Medium (CVSS 3.x base score 6.5)
CVSS v2: 4.0
EPSS exploit prediction: 1% (63rd percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-20
Affected product: Mongodb
Published: 2021-12-15
Last modified: 2026-06-17

Description

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.

Frequently asked questions

What is CVE-2021-20330?: 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.
How severe is CVE-2021-20330?: CVE-2021-20330 has a CVSS 3.x base score of 6.5, rated medium severity. It is exploitable over network with low attack complexity, requires low privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.
Is CVE-2021-20330 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (63rd percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-20330?: CVE-2021-20330 affects Mongodb. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2021-20330?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
When was CVE-2021-20330 published?: CVE-2021-20330 was published on 2021-12-15 and last updated on 2026-06-17.

References

https://jira.mongodb.org/browse/SERVER-36263

Affected products (1)

cpe:2.3:a:mongodb:mongodb:*:*:*:*:*:*:*:*

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Threat intelligence

Threat-intel indicators referencing this CVE:

160.202.253.14 (ipv4-addr)
122.154.58.9 (ipv4-addr)
122.13.25.55 (ipv4-addr)
120.198.23.233 (ipv4-addr)
203.154.34.104 (ipv4-addr)
91.208.207.34 (ipv4-addr)
49.115.217.120 (ipv4-addr)
49.233.137.179 (ipv4-addr)