Heap over-read or silent misparse via 32-bit truncation of JSON length in BSON JSON parser (CVE-2026-84970) | HOL Guard CVE

Unknown severity · Source severity not reportedCVE-2026-84970

Heap over-read or silent misparse via 32-bit truncation of JSON length in BSON JSON parser

Answer in brief

CVE-2026-84970 records a Unknown severity vulnerability in Heap over-read or silent misparse via 32-bit truncation of JSON length in BSON JSON parser. 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

A numeric truncation weakness exists in the JSON parsing component of the MongoDB C++ Driver's BSON library. An actor who controls the text that an embedding application hands to the library's public JSON parsing interface, when that text is very large, can cause the library to read memory beyond the supplied buffer and return it to the caller, to silently accept only part of the input as a complete document, or to terminate the process. No MongoDB server, credentials, or non-default configuration is required; the effect is confined to the process that uses the library.

Quoted source text, attributed separately from HOL analysis.