CVE-2026-18691
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.
Scoring
- Severity
- CRITICAL
- CVSS base score
- 9
- CVSS vector
- 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
- EPSS probability
- 0.24%
- CWE
- CWE-757
- Published
- 2026-08-11
- Last modified
- 2026-08-11
Affected products
- MongoDB MongoDB Server
- MongoDB MongoDB Server
- MongoDB MongoDB Server
Weakness type
Related vulnerabilities
- CVE-2026-72889 — Net::OAuth versions before 0.33 for Perl allow the sender to choose the signature algorithm in verify
- CVE-2026-72887 — Net::OAuth::Client versions before 0.32 for Perl allow the service provider to silently downgrade OAuth 1.0a to OAuth 1.0 in get_request_token
- CVE-2026-55953 — TLS 1.2 and DTLS client accepts unoffered anonymous cipher suite, bypassing server authentication
- CVE-2026-4942 — IBM i is Affected by Algorithm Downgrade in Transport Layer Security []
- CVE-2026-53712 — SCRAM: Silent channel-binding authentication downgrade via unsupported certificate algorithms
- CVE-2026-48747 — Symfony: Mailomat Mailer Webhook Parser Reads the HMAC Algorithm from the Request: Signature Algorithm Downgrade
- CVE-2026-54780 — CoreWCF: WS-Security Reference DigestMethod Algorithm-Suite Bypass
- CVE-2026-54291 — Silent channel-binding authentication downgrade via unsupported certificate algorithms