CVE-2026-81521 Cross-database write retargeting via unvalidated dotted database name in Client.BulkWrite in the MongoDB Go Driver
An attacker can redirect bulk write operations to unintended databases by supplying unvalidated dotted names, potentially modifying unauthorized data.
- 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-2026-81521?
CVE-2026-81521 is a high-severity vulnerability in MongoDB GO Driver, published on 27 Aug 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Official description
The MongoDB Go Driver's client-level bulk write operation may accept a caller-supplied database name containing a reserved separator character without escaping it before the name is used to build the target namespace for the operation. An application that passes untrusted input as a database name could therefore have the write directed at a database and collection other than the ones it intended. Only the Client.BulkWrite API is affected.
Weakness: CWE-99
Which versions are affected by CVE-2026-81521?
It affects 1 product.
Products include Mongodb Go Driver.
How do I fix CVE-2026-81521?
Upgrade to a fixed version.
Is CVE-2026-81521 being exploited?
There is no known exploitation of CVE-2026-81521 in the wild and no public exploit code.
Other vulnerabilities in MongoDB GO Driver
- CVE-2026-107324 Application denial of service via integer overflow in BSON value-length validation in MongoDB Go Driver
- CVE-2026-107325 Application denial of service via missing BSON array length validation in MongoDB Go Driver
- CVE-2021-20329 Specific cstrings input may not be properly validated in the Go Driver
- CVE-2026-88031 GridFS data deletion via query-operator injection in file IDs in the MongoDB Go Driver
Sources
Also known as DEBIAN-CVE-2026-81521, UBUNTU-CVE-2026-81521.