CVE-2026-18691

EUVD-2026-56921
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.
Algorithm Downgrade
ProviderTypeBase ScoreAtk. VectorAtk. ComplexityPriv. RequiredVector
NISTPrimary
8.8 HIGH
ADJACENT_NETWORK
LOW
NONE
CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Base Score
CVSS 3.x
EPSS Score
Percentile: 26.61%
Affected Products (NVD)
VendorProductVersion
mongodbmongodb
7.0.0 ≤
𝑥
< 7.0.40
mongodbmongodb
8.0.0 ≤
𝑥
< 8.0.29
mongodbmongodb
8.2.0 ≤
𝑥
≤ 8.2.12
mongodbmongodb
8.3.0 ≤
𝑥
< 8.3.8
mongodbmongodb
9.0.0:alpha0
mongodbmongodb
9.0.0:alpha1
mongodbmongodb
9.1.0:alpha0
𝑥
= Vulnerable software versions
Ubuntu logo
Ubuntu Releases
Ubuntu Product
Codename
mongodb
bionic
needs-triage
focal
needs-triage
jammy
dne
noble
dne
resolute
dne
trusty
needs-triage
xenial
needs-triage