# CVE-2026-107457: Qt QMqttClient memory corruption in MQTT 5

Source: https://junglewise.ai/threats/cve-2026-107457-a-memory-corruption-vulnerability-in-the-qmqttclient-class-of  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-11-02. Updated: 2026-11-02  
License: CC BY 4.0 with a link back

CVE-2026-107457 · Severity: info · Published 2026-11-02

The Qt MQTT library's QMqttClient component handles MQTT protocol connections for IoT and messaging applications. Under specific MQTT 5 connection settings, the component can corrupt memory, causing applications to crash and become unavailable. This primarily affects system availability rather than exposing sensitive data.

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

## Quick answers

**Is CVE-2026-107457 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-107457 being exploited in the wild.

**How severe is CVE-2026-107457?** Informational severity, published 2 November 2026.

**Which products and versions are affected?** Qt 5.12.0 to 6.8.8, 6.9.0 to 6.11.2.

**Is there a fix for CVE-2026-107457?** Yes: fixed in Qt 6.8.9, Qt 6.11.3, Qt 6.12.0. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-107457 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-107457?** Check whether you run Qt at an affected version. 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.

## How to fix

- Fixed in Qt 6.8.9, Qt 6.11.3, Qt 6.12.0

## Technical details

A memory corruption vulnerability exists in the QMqttClient class when processing certain MQTT 5 connection configurations between client and server. The vulnerability can be triggered by an attacker controlling the server or intercepting the connection to send malicious MQTT 5 protocol settings. Exploitation results in a denial of service through application crash; a fix is available in Qt 6.8.9, 6.11.3, and 6.12.0.

## Affected products

- Qt Qt 5.12.0 to 6.8.8, 6.9.0 to 6.11.2

## Timeline

- 2026-11-02: disclosed

## References

- [https://codereview.qt-project.org/c/qt/qtmqtt/+/762286](https://codereview.qt-project.org/c/qt/qtmqtt/+/762286)
- [https://wiki.qt.io/List_of_known_vulnerabilities_in_Qt_products](https://wiki.qt.io/List_of_known_vulnerabilities_in_Qt_products)

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