VulnerabilityPublished 11 Nov 2026

CVE-2026-126495: emqx MQTTX · Cross-site Scripting

Affects emqx MQTTXSource CVE Database V5

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Not known to be exploited · CVSS 5.3 Medium.

Data as of 11 Nov 2026, 02:03 UTC

CVSS 4.0 base score

5.3Medium

How severe the flaw is on the 0–10 CVSS scale.

Thin evidence

One scorer or none

CVSS scores by source
CNA (VulnCheck)	CVSS 4.0	5.3
CNA (VulnCheck)	CVSS 3.1	6.1

CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N

Attack Vector: Network
Attack Complexity: Low
Attack Requirements: None
Privileges Required: None
User Interaction: Passive
Vulnerable system confidentiality: None
Vulnerable system integrity: None
Vulnerable system availability: None
Subsequent system confidentiality: Low
Subsequent system integrity: Low
Subsequent system availability: None

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable system is bound to the network stack and the set of possible attackers extends beyond the other options listed below, up to and including the entire Internet. Such a vulnerability is often termed “remotely exploitable” and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: Low: The attacker must take no measurable action to exploit the vulnerability. The attack requires no target-specific circumvention to exploit the vulnerability. An attacker can expect repeatable success against the vulnerable system.
Attack Requirements: None: The successful attack does not depend on the deployment and execution conditions of the vulnerable system. The attacker can expect to be able to reach the vulnerability and execute the exploit under all or most instances of the vulnerability.
Privileges Required: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files of the vulnerable system to carry out an attack.
User Interaction: Passive: Successful exploitation of this vulnerability requires limited interaction by the targeted user with the vulnerable system and the attacker’s payload. These interactions would be considered involuntary and do not require that the user actively subvert protections built into the vulnerable system.
Vulnerable system confidentiality: None: There is no loss of confidentiality within the Vulnerable System.
Vulnerable system integrity: None: There is no loss of integrity within the Vulnerable System.
Vulnerable system availability: None: There is no impact to availability within the Vulnerable System.
Subsequent system confidentiality: Low: There is some loss of confidentiality. Access to some restricted information is obtained, but the attacker does not have control over what information is obtained, or the amount or kind of loss is limited. The information disclosure does not cause a direct, serious loss to the Subsequent System.
Subsequent system integrity: Low: Modification of data is possible, but the attacker does not have control over the consequence of a modification, or the amount of modification is limited. The data modification does not have a direct, serious impact to the Subsequent System.
Subsequent system availability: None: There is no impact to availability within the Subsequent System or all availability impact is constrained to the Vulnerable System.

Definitions: FIRST CVSS v4.0 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 11 Nov 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 10 Nov 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponized: A Metasploit exploit module or Exploit-DB entry exists (Metasploit scanner modules do not count), or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Affected software

Product	Affected	Fixed in
emqxMQTTX	Affected <=1.13.3	Fixed in–
GitHubMQTTX`pkg:github/MQTTX`Other threats	Affected <=1.13.3	Fixed in–

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AI-suggested

Users should verify with the vendor for updates or patches addressing this vulnerability. Until a fix is available, users should exercise caution when connecting to untrusted MQTT brokers or subscribing to untrusted topics. Monitoring vendor advisories for official remediation guidance is recommended. Since this is a client-side vulnerability requiring user interaction, limiting exposure to untrusted sources can reduce risk.

Description

MQTTX desktop versions up to 1.13.3 have a stored cross-site scripting (XSS) vulnerability. This flaw allows attackers to inject malicious scripts via MQTT topic names or payloads that are rendered without proper escaping in tooltips. When a user hovers over affected Topic Tree or JSON tree nodes, the malicious script executes in the Electron renderer environment, which has nodeIntegration enabled, increasing potential impact.

Impact

Successful exploitation allows an attacker to execute arbitrary scripts in the context of the MQTTX desktop application. This could lead to unauthorized actions or data exposure within the client environment. The risk is elevated by the Electron renderer's nodeIntegration feature, which can increase the attack surface. However, exploitation requires the victim to interact by hovering over the malicious tooltip, and the attacker must control the MQTT broker or be able to publish to topics the victim subscribes to.

Summary

CVE-2026-126495 describes a stored cross-site scripting vulnerability in MQTTX desktop client versions up to and including 1.13.3. The vulnerability arises because MQTT topic names or payloads published to the client are rendered unescaped in tooltips within the application UI. An attacker who controls an MQTT broker or can publish to subscribed topics can inject JavaScript code that executes in the Electron renderer process. Since nodeIntegration is enabled, this script execution could lead to elevated risks within the client environment. The CVSS 4.0 base score is 5.3 (medium severity), reflecting network attack vector, low complexity, no privileges required, and user interaction needed.

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 11 Nov 2026, 02:03 UTC

Technical details

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