# CVE-2026-120807: Privilege escalation via fail-open user lookup in X.509 cluster-membership guard

Status: published. Published: 2026-11-10. Updated: 2026-11-13.

A flaw in MongoDB’s X.509 cluster-membership authentication guard could allow a holder of a cluster-member certificate to gain elevated internal privileges when a specific deployment configuration is in use. An internal check, which prevents a certificate recognized as a cluster member from also being treated as a regular user, does not correctly distinguish between certain error conditions encountered during user lookup. Under certain timing conditions, this can cause the check to be bypassed, granting the connection full internal system privileges. Triggering this issue requires possession of a valid cluster-member TLS certificate, non-default X.509 cluster authentication configuration, and specific conditions during the user cache lookup process.

## Remediation

No remediation reported in collected sources

## Affected products and versions

- MongoDB / MongoDB Server: ≥ 9.0.0; < 9.0.7 (affected, semver); ≥ 8.3.0; < 8.3.16 (affected, semver); ≥ 8.0.0; < 8.0.37 (affected, semver); ≥ 7.0.0; < 7.0.48 (affected, semver). Source: CNA: mongodb

## Severity and prioritization

- CVSS 4.0: 7.5 (high); CVSS:4.0/AV:N/AC:H/AT:P/PR:H/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N; source: CNA: mongodb

- CVSS 3.1: 6.6 (medium); CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:U/C:H/I:H/A:H; source: CNA: mongodb

- CVSS 4.0: 7.5 (high); CVSS:4.0/AV:N/AC:H/AT:P/PR:H/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/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; source: NVD: cna@mongodb.com

- CVSS 3.1: 6.6 (medium); CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:U/C:H/I:H/A:H; source: NVD: cna@mongodb.com

- CISA KEV: No listing in collected sources

- EPSS: 0.23% as of 2026-11-13; percentile 13.55%

- SSVC: exploitation poc; automatable no; technical impact total; source ADP: CISA-ADP

- Weaknesses: CWE-754

## Exploit evidence

- exploit: https://jira.mongodb.org/browse/SERVER-130169 (ADP: CISA-ADP)

## References

- https://jira.mongodb.org/browse/SERVER-130169 (CNA: mongodb)

- https://jira.mongodb.org/browse/SERVER-130169 (ADP: CISA-ADP; exploit)

- https://jira.mongodb.org/browse/SERVER-130169 (cna@mongodb.com)

## Provenance

- CNA: mongodb: https://www.cve.org/CVERecord?id=CVE-2026-120807; retrieved 2026-11-13; source updated 2026-11-13

- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-120807; retrieved 2026-11-11; source updated 2026-11-10

- FIRST EPSS: https://api.first.org/data/v1/epss?cve=CVE-2026-120807; retrieved 2026-11-13; source updated Not reported

Revision: 565edf896c6b0211ea7a1aa3098e844c44610c47991a52058887fa46e2d0f33b

Canonical: https://y2.dev/cve/CVE-2026-120807

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