CVE-2026-71194
Description
A flaw was found in the OpenStack Designate mDNS NOTIFY handler. The _handle_notify method performs zone lookups without pool_id scoping, unlike the QUERY and AXFR handlers which were previously updated to be pool-aware. When zones with the same name exist across different DNS pools, the storage layer finds multiple matches and raises a NotFound exception, causing all NOTIFY processing for the affected zone name to fail. This results in denial of service for DNS zone transfer notifications, causing stale zone data on secondary DNS servers. The mDNS NOTIFY path is reachable via unauthenticated UDP on port 5354.
Statement
Red Hat OpenStack Platform (RHOSP) ships Designate across multiple versions. The mDNS NOTIFY handler DoS can occur whenever zone names collide across pools, regardless of how the colliding zones were created. However, in default configurations, only a single pool is used, making collisions unlikely without administrator action or exploitation of CVE-2026-71193. Multipool deployments using the AttributeFilter scheduler were never a fully supported configuration in any RHOSP version.
In RHOSP 13, 16.2, and 17.1 (TripleO deployment), the mDNS service listens on port 5354/UDP by default and does not require authentication for the NOTIFY handler path.
For Red Hat OpenStack Services on OpenShift (RHOSO, openstack-18.0), the mDNS service defaults to a ClusterIP service type with no NodePort or LoadBalancer exposure, making port 5354 reachable only within the OpenShift cluster network. This significantly limits the attack surface for the mDNS DoS.
Mitigation
Restrict network access to the mDNS service port (default 5354/UDP and TCP) using firewall rules, allowing only traffic from known DNS master servers. Note that enabling the 'query_enforce_tsig' option does NOT protect the NOTIFY handler path, as it only applies to QUERY and AXFR operations.
To prevent the precondition of colliding zones: verify that the 'scheduler_filters' configuration option in the [service:central] section uses 'default_pool' (the default) or 'pool_id_attribute' instead of 'attribute'. This prevents unauthorized creation of zones in alternative pools.
Common Vulnerability Scoring System (CVSS) Score Details
Info alert:Important note
CVSS scores for open source components depend on vendor-specific factors (e.g. version or build chain). Therefore, Red Hat's score and impact rating can be different from NVD and other vendors. Red Hat remains the authoritative CVE Naming Authority (CNA) source for its products and services (see Red Hat classifications).
The following CVSS metrics and score provided are preliminary and subject to review.
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 4.3 | N/A | 6.8 |
| Attack Vector | Network | N/A | Network |
| Attack Complexity | Low | N/A | High |
| Privileges Required | Low | N/A | None |
| User Interaction | None | N/A | None |
| Scope | Unchanged | N/A | Changed |
| Confidentiality | None | N/A | None |
| Integrity Impact | None | N/A | None |
| Availability Impact | Low | N/A | High |
Vector
Red Hat: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L
cve.org: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:N/I:N/A:H
Red Hat CVSS v3 Score Explanation
mDNS NOTIFY handler performs pool-blind zone lookup causing deterministic failure when colliding zones exist across pools. Requires authenticated access to create colliding zones.
Understanding the Weakness (CWE)
Confidentiality
Technical Impact: Read Application Data; Read Files or Directories
An attacker could bypass intended access restrictions to read sensitive data, either by reading the data directly from a data store that is not correctly restricted, or by accessing insufficiently-protected, privileged functionality to read the data.
Integrity
Technical Impact: Modify Application Data; Modify Files or Directories
An attacker could bypass intended access restrictions to modify sensitive data, either by writing the data directly to a data store that is not correctly restricted, or by accessing insufficiently-protected, privileged functionality to write the data.
Access Control
Technical Impact: Gain Privileges or Assume Identity; Bypass Protection Mechanism
An attacker could bypass intended access restrictions to gain privileges by modifying or reading critical data directly, or by accessing privileged functionality.
Confidentiality,Integrity,Availability
Technical Impact: Execute Unauthorized Code or Commands
An attacker could use elevated privileges to execute unauthorized commands or code.
Availability
Technical Impact: DoS: Crash, Exit, or Restart; DoS: Resource Consumption (CPU); DoS: Resource Consumption (Memory); DoS: Resource Consumption (Other)
An attacker could gain unauthorized access to resources on the system and excessively consume those resources, leading to a denial of service.
Acknowledgements
Upstream acknowledges Omer Schwartz (Red Hat) and Tore Anderson (Redpill Linpro AS) as the original reporters.
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