CVE-2021-32040 Large aggregation pipelines with a specific stage can crash mongod under default configuration
An attacker can crash the MongoDB server by submitting a specially crafted, extremely long aggregation pipeline, causing a stack overflow.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2021-32040?
CVE-2021-32040 is a medium-severity denial of service vulnerability in Mongodb Mongodb, published on 12 Apr 2022. Any signed-in user can exploit it over the network, with no action from the victim.
Official description
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.
Which versions are affected by CVE-2021-32040?
1 open source package ship an affected version, including mongodb. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
mongodb Bitnami | From 4.2.0 | 4.2.16, 4.4.11, 5.0.4 |
Products include Mongodb Mongodb.
How do I fix CVE-2021-32040?
Upgrade mongodb to a fixed version for your release line: 4.2.16, 4.4.11 or 5.0.4.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2021-32040 being exploited?
There is no known exploitation of CVE-2021-32040 in the wild and no public exploit code.
Other vulnerabilities in Mongodb Mongodb
- CVE-2025-14847 MongoDB and MongoDB Server Improper Handling of Length Parameter Inconsistency
- CVE-2026-82067 Auth bypass in MongoDB Server
- CVE-2026-13072 MongoDB Improper Input Validation in Compute Mode External Data Processing Leading to Memory Corruption
- CVE-2017-15535 Denial of service in n/a
- CVE-2026-18691 Improper Authentication in MongoDB Intra-Cluster Connections Allows Credential Exposure
Sources
Also known as BIT-mongodb-2021-32040, GHSA-hmq6-2xj3-79w5, UBUNTU-CVE-2021-32040.