# CVE-2026-120749: D-Bus daemon denial of service via monitored broadcast message failure

Source: https://junglewise.ai/threats/cve-2026-120749-a-flaw-was-found-in-d-bus-with-a-privileged-monitoring-client  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-11-06. Updated: 2026-11-06  
License: CC BY 4.0 with a link back

CVE-2026-120749 · Severity: medium · CVSS 6.2 · Published 2026-11-06

D-Bus is a system messaging daemon that allows processes on a Linux system to communicate with each other. An unprivileged user can crash the D-Bus daemon if a privileged monitoring tool (such as dbus-monitor) is actively running, causing a denial of service that disrupts all applications relying on the message bus. This requires the presence of an active monitoring client, which is typically a privileged operation.

Vendors: [Freedesktop](https://junglewise.ai/threats/vendors/freedesktop).

## Quick answers

**Is CVE-2026-120749 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-120749 being exploited in the wild.

**How severe is CVE-2026-120749?** Medium severity, with a CVSS score of 6.2, published 6 November 2026.

**Which products and versions are affected?** freedesktop D-Bus.

**Is there a fix for CVE-2026-120749?** No fixed version is recorded yet. This vulnerability can only be exploited when a privileged monitoring process such as dbus-monitor or busctl monitor is actively running on the affected dbus-daemon instance. If no monitoring process is active, the vulnerable code path is not reached. 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-2026-120749 attacked?** It is attacked with local access, in a software library.

**Am I affected by CVE-2026-120749?** Check whether you run Freedesktop D-Bus. 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


This vulnerability can only be exploited when a privileged monitoring process such as dbus-monitor or busctl monitor is actively running on the affected dbus-daemon instance. If no monitoring process is active, the vulnerable code path is not reached.

## Technical details

The vulnerability is a reachable assertion (CWE-617) in dbus-daemon triggered when a driver-originated broadcast message cannot be delivered to a monitored recipient. The flaw occurs because driver broadcasts use serial 0; when delivery fails and the daemon attempts to compose a monitor error reply, it asserts reply_serial != 0, causing the daemon to abort. This is an incomplete fix for CVE-2023-34969. The attack requires an unprivileged local user and an active privileged monitoring process on the same bus.

## Affected products

- freedesktop D-Bus

## Timeline

- 2026-11-06: disclosed

## References

- [https://access.redhat.com/downloads/content/package-browser/](https://access.redhat.com/downloads/content/package-browser/)
- [https://access.redhat.com/security/cve/CVE-2026-120749](https://access.redhat.com/security/cve/CVE-2026-120749)