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CWE-501Weakness · CWE-501

CVE-2026-44091

CRITICAL · 9.1 CVSS v3.1 Published 2026-07-30
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
100/100
Remediation priority · Urgent
Remotely reachable No privileges Zero-click 3 weeks old

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
An unauthenticated remote attacker can post a malicious ID to the MQTT Broker results in the creation of a new configuration entry in the system configuration. This may lead to integrity and availability loss.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · moderate confidence

This vulnerability allows unauthenticated remote attackers to send specially crafted MQTT messages containing malicious IDs to the broker. The broker improperly processes these messages, resulting in unauthorized creation of new configuration entries in the system's configuration store. This allows attackers to modify system behavior, leading to integrity compromise through unauthorized configuration changes and potential availability disruption.

MitigationImplement authentication and authorization on the MQTT broker, apply input validation and sanitization on all MQTT message payloads before processing, and restrict network access to the broker to prevent unauthenticated access.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
High
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Verify MQTT broker authentication is enabled
    Check your MQTT broker configuration file (e.g., mosquitto.conf, emqx.conf, or broker-specific config) for authentication settings. Look for 'allow_anonymous', 'password_file', or authentication plugins. Run: grep -i 'allow_anonymous' /etc/mosquitto/mosquitto.conf or equivalent for your broker.
    Affected if allow_anonymous is set to true or no authentication mechanism is configured
  2. Identify if MQTT port is exposed to untrusted networks
    Check firewall rules or network ACLs. Run: netstat -tlnp | grep -E '1883|8883' or check cloud security groups. Determine if the MQTT port is accessible from IP addresses outside your trusted network.
    Affected if MQTT port 1883 (or 8883 for TLS) is open to 0.0.0.0/0 or untrusted IP ranges
  3. Review broker logs for unauthenticated connection attempts
    Examine MQTT broker logs (typically in /var/log/mosquitto/, /var/log/emqx/, or journalctl -u mosquitto). Search for connection events from unknown clients: grep -i 'connection' /var/log/mosquitto/mosquitto.log | head -100
    Affected if Logs show connections from client IDs you do not recognize or connections without authentication credentials
  4. Inspect for unauthorized configuration entries
    Review your broker's configuration persistence (retained messages, $SYS topics, or any configuration stores). For persistent clients, query the broker's client database or check retained message topics: mosquitto_sub -t '#' -v -C 1 (with appropriate credentials)
    Affected if There are retained messages or configuration entries with client IDs or topics that were not created by your authorized systems
  5. Check for unexpected client IDs in the broker
    Use broker management tools to list connected or registered clients. For Mosquitto: mosquitto_ctrl -u admin -P password brokers local clients. Compare against your known authorized clients and services.
    Affected if Client IDs exist that correspond to systems or devices you did not register
  6. Verify input validation on configuration-related MQTT messages
    Review your application code or broker ACL policies that process MQTT messages for configuration changes. Check if there are ACL rules limiting which topics clients can publish to. Run: grep -i 'acl' /etc/mosquitto/mosquitto.conf
    Affected if No ACL policies exist or configuration topics are writable by anonymous clients

Your environment is affected if the MQTT broker allows anonymous connections and is accessible from untrusted networks, or if unauthorized configuration entries exist in the broker's client database or retained messages.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

From vendor data
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Implement authentication and authorization on the MQTT broker, apply input validation and sanitization on all MQTT message payloads before processing, and restrict network access to the broker to prevent unauthenticated access.

Have this fixed Scoped from the published advisory
  • Consultation4.0 h
  • Implementation6.0 h
  • Testing4.0 h
  • Review / QA3.0 h
17.0 hours of engineering $3,020
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2026-44091 in production — separate from our analysis above.

No notes yet

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
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