# CVE-2026-128886: Dbus: server accept watch can be stalled by blocking nonce-tcp accept_with_noncefile path

Status: published. Published: 2026-11-13. Updated: 2026-11-13.

A flaw was found in dbus when configured with the nonce-tcp transport. An unauthenticated attacker able to connect to an exposed listener can cause a Denial of Service (DoS) by opening a connection and withholding the expected authentication token. Because the server processes this verification without enforcing a timeout, the stalled connection blocks the accept process and prevents legitimate clients from establishing new connections.

## Remediation

- workaround: Disable non-standard `nonce-tcp` listeners in the D-Bus configuration in favor of standard UNIX domain sockets. If network reachability is required, restrict access to trusted hosts using `firewalld`.

To remove an exposed port from an untrusted firewall zone:

```
firewall-cmd --permanent --zone=public --remove-port=<PORT>/tcp
firewall-cmd --permanent --zone=trusted --add-source=<TRUSTED_IP_OR_SUBNET>
firewall-cmd --reload
```

Caveats:
Restricting or disabling network listeners prevents remote clients outside the trusted subnet from connecting to the affected bus.

Warning:
Reloading the firewall rules or altering the D-Bus server configuration requires restarting the affected D-Bus service, which will drop existing connections and temporarily disrupt communications. (source: CNA: redhat)

## Affected products and versions

- Red Hat / Red Hat Enterprise Linux 10 (dbus): Version range not reported. Source: CNA: redhat

## Severity and prioritization

- CVSS 3.1: 6.2 (medium); CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H; source: CNA: redhat

- CVSS 3.1: 6.2 (medium); CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H; source: NVD: secalert@redhat.com

- CISA KEV: No listing in collected sources

- EPSS: Not available

- SSVC: Not available

- Weaknesses: CWE-1322

## Exploit evidence

No exploit evidence in collected sources. This is not proof of no exploitation.

## References

- https://access.redhat.com/security/cve/CVE-2026-128886 (CNA: redhat; vdb-entry, x_refsource_REDHAT)

- https://bugzilla.redhat.com/show_bug.cgi?id=2472930 (CNA: redhat; issue-tracking, x_refsource_REDHAT)

- https://access.redhat.com/security/cve/CVE-2026-128886 (secalert@redhat.com)

- https://bugzilla.redhat.com/show_bug.cgi?id=2472930 (secalert@redhat.com)

## Provenance

- CNA: redhat: https://www.cve.org/CVERecord?id=CVE-2026-128886; retrieved 2026-11-13; source updated 2026-11-13

- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-128886; retrieved 2026-11-14; source updated 2026-11-13

Revision: b2b2ad7ee661ab4b99a7d59616f4efbf043bbeceef4d4d91867779c3d7efa2ae

Canonical: https://y2.dev/cve/CVE-2026-128886

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