CVE-2026-18691 Improper Authentication in MongoDB Intra-Cluster Connections Allows Credential Exposure
An attacker with network access can force weaker authentication in MongoDB clusters to steal internal credentials and gain superuser access.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-18691?
CVE-2026-18691 is a critical authentication bypass vulnerability in Mongodb Mongodb, published on 11 Aug 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
An issue in MongoDB Server's intra-cluster connection setup could allow a party with suitable network access to influence which authentication mechanism is used when one replica set member connects to another. Under certain conditions, this could cause the cluster's shared internal credential to be transmitted in a less-protected form, potentially allowing that credential to be recovered. If recovered, the credential could be used to authenticate as the internal superuser to nodes in the deployment.
Weakness: CWE-757
Which versions are affected by CVE-2026-18691?
1 open source package ship an affected version, including mongodb. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
mongodb Bitnami | From 7.0.0 | 7.0.40, 8.0.29, 8.3.8, 9.0.2 |
Products include Mongodb Mongodb.
How do I fix CVE-2026-18691?
Upgrade mongodb to a fixed version for your release line: 7.0.40, 8.0.29, 8.3.8 or 9.0.2.
Upgrade, and rotate credentials and sessions that may have been exposed. More about Authentication bypass.
Is CVE-2026-18691 being exploited?
There is no known exploitation of CVE-2026-18691 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-2024-1351 MongoDB Server may allow successful untrusted connection
Sources
Also known as BIT-mongodb-2026-18691, GHSA-jx4v-jf9c-3rh7, MINI-9rvh-8jjx-56rv, MINI-hq2m-3h6f-vw76, MINI-jjf8-v5j5-pvjh, MINI-r99w-g6f3-wmph and 1 more.