Security readout for executives and security teams
Plain-English summary
A network-adjacent attacker may be able to weaken authentication between MongoDB replica-set members and expose the cluster’s shared internal credential. Recovering that credential could provide internal-superuser access across affected nodes, creating serious confidentiality, integrity, and availability risk.
Executive priority
Prioritize immediate assessment of listed MongoDB deployments, especially clusters with weak inter-node isolation. Obtain MongoDB’s confirmed remediation and schedule upgrades promptly. Treat suspected credential exposure as a cluster-wide privileged-access incident, while recognizing that the supplied evidence does not establish active exploitation.
Technical view
CVE-2026-18691 is a CWE-757 authentication-mechanism downgrade affecting listed MongoDB Server versions or families 8.3.0, 8.0, and 7.0. An attacker with suitable network access could influence intra-cluster authentication negotiation, potentially exposing the shared credential in a less-protected form. Successful recovery enables internal-superuser authentication.
Likely exposure
Exposure is most concerning where untrusted systems can reach or influence replica-set member connections. The supplied record lists 8.3.0, 8.0, and 7.0, but does not define affected patch ranges or fixed versions. Strong network isolation reduces opportunity but does not establish that a deployment is unaffected.
Exploitation context
The CVSS 4.0 score is 9.0 with adjacent-network access, low complexity, no privileges, and no user interaction. Additional attack conditions are required. The supplied sources provide no evidence of active exploitation, and the CVE is not listed as KEV in the bundle.
Researcher notes
The central issue is authentication downgrade during intra-cluster connection setup, not ordinary application-user authentication. Validation should focus on network influence over replica-set traffic, mechanism selection, and shared-credential scope. The bundle does not identify fixed releases, observable indicators, proof-of-concept availability, or confirmed attacks.
Mitigation direction
- Consult MongoDB SERVER-130264 for vendor-confirmed fixed versions and upgrade instructions.
- Restrict replica-set traffic to trusted hosts and isolated network paths.
- Prevent untrusted systems from reaching or influencing intra-cluster connections.
- If exposure is suspected, follow MongoDB guidance when replacing the shared internal credential.
- Monitor for unexpected internal-superuser authentication and abnormal inter-node authentication behavior.
Validation and detection
- Inventory MongoDB Server deployments using the listed 8.3.0, 8.0, and 7.0 versions or families.
- Map all systems able to access replica-set members or their inter-node network paths.
- Confirm precise affected patch levels and remediation against current MongoDB guidance.
- Review authentication logs for unexpected internal-superuser activity or unusual mechanism negotiation.
- If suspicious activity exists, scope every node sharing the potentially exposed credential.
Public sources used
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
Conservative CVE-to-ATT&CK context
These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.
ATT&CK lookup starting points
Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.
CWE-757: Exact CWE lookup
Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.
Open ATT&CK lookupCredential and access behavior lookup
The CVE wording references authentication or credential exposure, so valid-account and credential-access review may help. This is a Glexia inferred lookup path, not an official MITRE, ATT&CK, or CVE Program mapping.
Open ATT&CK lookupCVE-2026-18691 mapping review
Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.
Open ATT&CK lookup- Severity
- Critical
- CVSS
- 9 (4.0)
- Known Exploited
- No
- Published
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
CNA and ADP enrichment extracted from CVE v5
These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.
SSVC decision data
CVSS vector scores
2 official scoresWe collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.
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——mongodbCVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H2.85.9mongodbVulnerability scoring details
Base CVSS 4.0 score
9CriticalVector: 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
Base CVSS 3.1 score
8.8HighVector: CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Vulnerability timeline
Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.
- CVE reservedCVE Program
The CVE ID was reserved by the assigning CNA.
- CVE publishedCVE Program
The CVE record was published.
- CVE updatedCVE Program
The CVE record metadata indicates this as the latest update time.
ADP provider summaries
Source materials
- CVE List V5 sourceCVE List V5
- https://jira.mongodb.org/browse/SERVER-130264CVE reference, mongodb
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.
Selection of Less-Secure Algorithm During Negotiation ('Algorithm Downgrade')
Selection of Less-Secure Algorithm During Negotiation ('Algorithm Downgrade') represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.