What is CVE-2021-32040?

CVE-2021-32040 is a medium-severity vulnerability in MongoDB, classified under Stack-based Buffer Overflow. CVSS score: 6.5/10. Published 2022-04-12.

How severe is CVE-2021-32040?

Medium severity. CVSS v3 base score is 6.5 out of 10.

Is CVE-2021-32040 known to be exploited?

1 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.

Buffer overflow in MongoDB

CVE-2021-32040

It may be possible to have an extremely long aggregation pipeline in conjunction with a specific stage/operator and cause a stack overflow due to the size of the stack frames used by that stage. If an attacker could cause such an aggregation to occur, they could maliciously crash MongoDB in a DoS attack. This vulnerability affects MongoDB Server v4.4 versions prior to and including 4.4.28, MongoDB Server v5.0 versions prior to 5.0.4 and MongoDB Server v4.2 versions prior to 4.2.16. Workaround: >= v4.2.16 users and all v4.4 users can add the --setParameter internalPipelineLengthLimit=50 instead of the default 1000 to mongod at startup to prevent a crash.

Vulnerability class: Buffer Overflow

Published 2022-04-12 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 6.5 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H.

EPSS exploit prediction

EPSS: 0.020 (80.1th percentile), scored 2026-10-02.

Low probability of exploitation in the next 30 days, but still tracked. 80th percentile — 80.1% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.021 · newest: 0.020 · change: -0.000

Affected products

MongoDB
MongoDB Inc. Server — versions 5.0, 4.4, 4.2

Weakness classification (CWE)

Public proof-of-concept exploits

11notes/docker-unifi

References

jira.mongodb.org/browse/SERVER-58203 (Patch, Issue Tracking, Vendor Advisory)
jira.mongodb.org/browse/SERVER-59299 (Patch, Issue Tracking, Vendor Advisory)
jira.mongodb.org/browse/SERVER-60218 (Patch, Issue Tracking, Vendor Advisory)
security.netapp.com/advisory/ntap-20220609-0005/ (Third Party Advisory)

Frequently asked questions

What is CVE-2021-32040?: CVE-2021-32040 is a medium-severity vulnerability in MongoDB, classified under Stack-based Buffer Overflow. CVSS score: 6.5/10. Published 2022-04-12.
How severe is CVE-2021-32040?: Medium severity. CVSS v3 base score is 6.5 out of 10.
Is CVE-2021-32040 known to be exploited?: 1 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.