BSON element injection via NUL-embedded document keys in builder append (CVE-2026-84966) | HOL Guard CVE

Unknown severity · Source severity not reportedCVE-2026-84966

BSON element injection via NUL-embedded document keys in builder append

Answer in brief

CVE-2026-84966 records a Unknown severity vulnerability in BSON element injection via NUL-embedded document keys in builder append. The current sources do not mark it as known exploited. The current feed maps MongoDB/C++ Driver (generic). Check affected ranges and fixed versions before updating.

Analysis pending evidence review

HOL Guard separates source facts from reviewed analysis. See the methodology.

Published Sep 3, 2026Updated Sep 3, 2026Source checked Sep 3, 2026First seen by HOL Sep 3, 2026Material review Sep 3, 2026

Upstream Advisory

Key facts

Risk: Unknown severitySource severity not reported
Exploitation: Not marked as known exploited
Affected software: 1 mapped package or product
Fix availability: Available

Why this deserves its current priority

A CVSS score is not reported in the current record. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.

Analysis status

Analysis pending evidence review

Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.

Affected scope and exposure questions

The current feed maps MongoDB/C++ Driver (generic). Check affected ranges and fixed versions before updating.

Mapped affected packages and fixed versions
Package	Affected range	Fixed version
MongoDB/C++ Drivergeneric	>=3.2.0 <4.5.2	4.5.2

Recommended response

Check inventory. Check lockfiles and deployed manifests for MongoDB/C++ Driver.
Review the reported fix. Update MongoDB/C++ Driver to 4.5.2 if you use the affected versions. Test the change in a non-production environment first.

Evidence timeline and material changes

Published upstream
Sep 3, 2026
Evidence: source:cvelist:source_dates:source-dates:record
Source modified
Sep 3, 2026
Evidence: source:cvelist:source_dates:source-dates:record
First seen by HOL
Sep 3, 2026

Sources and claim methodology

Source referencejira.mongodb.org

Upstream source description

An incorrect numeric type conversion in the BSON document building component of the MongoDB C++ Driver may cause a length value to be interpreted incorrectly. When an application supplies an extremely large, non-terminated field name to the builder, the library may read memory outside the intended buffer and terminate the calling process. No authentication is required, but the calling application must pass the oversized name in a specific form.

Quoted source text, attributed separately from HOL analysis.