Cesanta Mongoose MQTT Broker main.c fn stack-based overflow (CVE-2026-101003) | HOL Guard CVE

Medium · CVSS 6.9CVE-2026-101003

Cesanta Mongoose MQTT Broker main.c fn stack-based overflow

Answer in brief

CVE-2026-101003 records a Medium severity (CVSS 6.9) vulnerability in Cesanta Mongoose MQTT Broker main.c fn stack-based overflow. The current sources do not mark it as known exploited. The current feed maps Cesanta/Mongoose (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 28, 2026Updated Sep 28, 2026Source checked Sep 28, 2026First seen by HOL Sep 28, 2026Material review Sep 28, 2026

Upstream Advisory

Key facts

Risk: Medium · CVSS 6.9
Exploitation: Not marked as known exploited
Affected software: 1 mapped package or product
Fix availability: Not reported

Why this deserves its current priority

CVSS is 6.9. 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 Cesanta/Mongoose (generic). Check affected ranges and fixed versions before updating.

Mapped affected packages and fixed versions
Package	Affected range	Fixed version
Cesanta/Mongoosegeneric	7.0 \|\| 7.1 \|\| 7.2 \|\| 7.3 \|\| 7.4 \|\| 7.5 \|\| 7.6 \|\| 7.7 \|\| 7.8 \|\| 7.9 \|\| 7.10 \|\| 7.11 \|\| 7.12 \|\| 7.13 \|\| 7.14 \|\| 7.15 \|\| 7.16 \|\| 7.17 \|\| 7.18 \|\| 7.19 \|\| 7.20 \|\| 7.21	Not reported

Recommended response

Check inventory. Check lockfiles and deployed manifests for Cesanta/Mongoose.
Review the reported fix. Monitor this advisory for an available fix and review any installs of the affected package.

Evidence timeline and material changes

Published upstream
Sep 28, 2026
Evidence: source:cvelist:source_dates:source-dates:record
Source modified
Sep 28, 2026
Evidence: source:cvelist:source_dates:source-dates:record
First seen by HOL
Sep 28, 2026

Sources and claim methodology

Upstream source description

A weakness has been identified in Cesanta Mongoose up to 7.21. Affected by this vulnerability is the function fn of the file tutorials/mqtt/mqtt-server/main.c of the component MQTT Broker. Executing a manipulation can lead to stack-based buffer overflow. The attack can be launched remotely. The exploit has been made available to the public and could be used for attacks. Upgrading to version 7.22 addresses this issue. This patch is called a9df523f76f43a38bd53b4232b9cfd4c16869e71. Upgrading the affected component is advised.

Quoted source text, attributed separately from HOL analysis.