# CVE-2026-103653: Qt CoAP out-of-bounds read in message parsing

Source: https://junglewise.ai/threats/cve-2026-103653-an-out-of-bounds-read-vulnerability-in-the-qt-coap-message  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-11-03. Updated: 2026-11-03  
License: CC BY 4.0 with a link back

CVE-2026-103653 · Severity: info · Published 2026-11-03

Qt CoAP is a library for building applications that use the Constrained Application Protocol (CoAP) to communicate with IoT devices and servers. A flaw in how it parses CoAP messages can cause applications to crash or operate with corrupted data if they receive a specially crafted malformed message.

Vendors: [Qt](https://junglewise.ai/threats/vendors/qt).

## Quick answers

**Is CVE-2026-103653 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-103653 being exploited in the wild.

**How severe is CVE-2026-103653?** Informational severity, published 3 November 2026.

**Which products and versions are affected?** Qt Qt CoAP.

**Is there a fix for CVE-2026-103653?** No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

**How is CVE-2026-103653 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-103653?** Check whether you run Qt CoAP. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

An out-of-bounds read vulnerability exists in QCoapInternalReply::createFromFrame() during CoAP message parsing. Processing a malformed CoAP message triggers the out-of-bounds read, leading to either a denial of service (crash) or potential data corruption. No authentication or user interaction is required; a network-adjacent attacker can send a malicious CoAP packet to trigger the flaw.

## Affected products

- Qt Qt CoAP

## Timeline

- 2026-11-03: disclosed

## References

- [https://codereview.qt-project.org/c/qt/qtcoap/+/760652](https://codereview.qt-project.org/c/qt/qtcoap/+/760652)
- [https://codereview.qt-project.org/c/qt/qtcoap/+/761120](https://codereview.qt-project.org/c/qt/qtcoap/+/761120)