Heap overflow via truncated base64 encoding of binary fields in length-limited JSON output (CVE-2026-84969) | HOL Guard CVE

Unknown severity · Source severity not reportedCVE-2026-84969

Heap overflow via truncated base64 encoding of binary fields in length-limited JSON output

Answer in brief

CVE-2026-84969 records a Unknown severity vulnerability in Heap overflow via truncated base64 encoding of binary fields in length-limited JSON output. 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	>=1.30.0 <1.30.9 \|\| >=2.0.0 <2.5.2	1.30.9, 2.5.2

Recommended response

Check inventory. Check lockfiles and deployed manifests for MongoDB/C Driver.
Review the reported fix. Update MongoDB/C Driver to 1.30.9 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 memory-handling error in the BSON-to-JSON conversion helpers of the MongoDB C Driver can write a small number of bytes past the end of a heap buffer when a binary field is encoded and the output is cut short at a caller-configured length limit. A party who supplies the document content, with no privileges on the application that links the driver, may cause a small amount of data outside the intended buffer to be altered.

Quoted source text, attributed separately from HOL analysis.