CVE-2026-18691

critical · 9

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.

CVSS

0.4%

EPSS (exploit prob.)

27th

EPSS percentile

2026-08-11

Published

CVSS:4.0/AV:A/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

Weaknesses

CWE-757

Affected products

Vendor	Product	Affected versions
mongodb	mongodb	>= 7.0.0, < 7.0.40
mongodb	mongodb	>= 8.0.0, < 8.0.29
mongodb	mongodb	>= 8.2.0, <= 8.2.12
mongodb	mongodb	>= 8.3.0, < 8.3.8
mongodb	mongodb	9.0.0
mongodb	mongodb	9.0.0
mongodb	mongodb	9.1.0

Check a specific version with /api/v1/cve/match.

References

https://jira.mongodb.org/browse/SERVER-130264

Query this programmatically:

curl https://evil-db.io/api/v1/cve/CVE-2026-18691