# CVE-2026-79680: Qt VNC Server authentication bypass in password mechanism

Source: https://junglewise.ai/threats/cve-2026-79680-authentication-bypass-vulnerability-in-the-password  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-09-24. Updated: 2026-09-26  
License: CC BY 4.0 with a link back

CVE-2026-79680 · Severity: info · Published 2026-09-24

Qt's VNC Server module, which allows remote sharing of Qt applications, contains a flaw in its password authentication mechanism. An attacker using a specially crafted VNC client that violates the standard RFB protocol can bypass password checks entirely and gain unauthorized remote access to shared applications, potentially exposing sensitive data or allowing malicious control of the application.

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

## Quick answers

**Is CVE-2026-79680 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-79680 being exploited in the wild.

**How severe is CVE-2026-79680?** Informational severity, published 24 September 2026.

**Which products and versions are affected?** Qt 6.4.0 to 6.8.8, 6.9.0 to 6.11.2.

**Is there a fix for CVE-2026-79680?** 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-2026-79680 attacked?** It is attacked over the network.

**Am I affected by CVE-2026-79680?** 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.

## Technical details

The Qt VNC Server module fails to properly validate RFB protocol compliance in the password authentication flow, allowing a non-conformant client to bypass authentication checks. An attacker can exploit this via network access without credentials or user interaction to gain unauthorized remote access to any Qt application exposing VNC sharing. A fix is available in Qt 6.8.9 and 6.11.3.

## Affected products

- Qt Qt 6.4.0 to 6.8.8, 6.9.0 to 6.11.2

## Timeline

- 2026-09-24: disclosed

## References

- [https://codereview.qt-project.org/c/qt/tqtc-qtvncserver/+/759160](https://codereview.qt-project.org/c/qt/tqtc-qtvncserver/+/759160)
- [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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