---
id: "CVE-2026-103653"
kind: "vulnerability"
aliases: ["CVE-2026-103653"]
title: "Qt CoAP: malformed message parsing reads out of bounds, crashing apps"
severity: "medium"
cvss: 6.7
epss: null
exploited: false
status: "open"
category: "package"
products: []
ecosystems: []
tags: ["c++", "coap", "package", "qt"]
not_affected_if: ["no-qt-coap-module"]
published_at: "2026-11-03T08:17:13+00:00"
first_seen_at: "2026-11-03T08:19:30+00:00"
updated_at: "2026-11-03T08:19:37+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-103653", "first_seen_at": "2026-11-03T08:19:30+00:00"}]
---

# Qt CoAP: malformed message parsing reads out of bounds, crashing apps

The Qt CoAP module reads past the end of a buffer when it parses a malformed CoAP message in QCoapInternalReply::createFromFrame(). An attacker who sends such a message can crash an application using Qt CoAP or make it act on incorrect data.

_Summary, check and fix written by a model from the sources; labelled as such._

## How to check

- Check whether an application links the Qt CoAP module (look for `Qt6CoAP` or `Qt5CoAP` in build files or dependencies).
- Check the installed Qt version with `qmake --version` or `qt-cmake --version`; the affected and fixed version ranges are unknown from the sources.

## Timeline

- 2026-11-03T08:19:30+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-103653

## From the sources

An out-of-bounds read vulnerability in the Qt CoAP message parsing (QCoapInternalReply::createFromFrame()) of the Qt CoAP module. Processing a malformed CoAP message can cause an application using Qt CoAP to crash (loss of availability) or to continue operating on incorrect data (potential loss of integrity).

---

_Free to read at a human pace. An API with keys and an MCP server are in preparation; early access: hello@infrastack.ai_