# CVE-2026-126838: Rust Driver public Client Debug output exposes CSFLE KMS master-key material

Status: published. Published: 2026-11-12. Updated: 2026-11-12.

A MongoDB Rust Driver component that holds client-side field level encryption settings includes key management service credential material in its diagnostic formatting output without redaction. An application that records or displays this formatted output may place that material where a party with read access to the application's diagnostic output can see it, which may result in unintended disclosure of key material.

## Remediation

No remediation reported in collected sources

## Affected products and versions

- MongoDB / Rust Driver: ≥ 3.9.0; < 3.9.1 (affected, semver); ≥ 3.8.0; < 3.8.2 (affected, semver); 3.7.0 (affected, semver); 3.6.0 (affected, semver); ≥ 3.5.0; < 3.5.2 (affected, semver); ≥ 3.4.0; < 3.4.1 (affected, semver); 3.3.0 (affected, semver); ≥ 3.2.0; < 3.2.5 (affected, semver); ≥ 3.1.0; < 3.1.1 (affected, semver); ≥ 3.0.0; < 3.0.1 (affected, semver); ≥ 2.8.0; < 2.8.2 (affected, semver); ≥ 2.7.0; < 2.7.1 (affected, semver); ≥ 2.6.0; < 2.6.1 (affected, semver); 2.5.0 (affected, semver); 2.4.0 (affected, semver). Source: CNA: mongodb

## Severity and prioritization

- CVSS 4.0: 5.7 (medium); CVSS:4.0/AV:L/AC:L/AT:P/PR:L/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N; source: CNA: mongodb

- CVSS 3.1: 5.5 (medium); CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N; source: CNA: mongodb

- CISA KEV: No listing in collected sources

- EPSS: Not available

- SSVC: Not available

- Weaknesses: CWE-532

## Exploit evidence

No exploit evidence in collected sources. This is not proof of no exploitation.

## References

- https://jira.mongodb.org/browse/RUST-2531 (CNA: mongodb)

## Provenance

- CNA: mongodb: https://www.cve.org/CVERecord?id=CVE-2026-126838; retrieved 2026-11-12; source updated 2026-11-12

Revision: b7d0b07fffd0dc6a1c508c8072c41afc26b45d61598509a15d838ff1685edba7

Canonical: https://y2.dev/cve/CVE-2026-126838

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Collected public records only. Check source status for coverage and freshness.