CVE-2026-94373 in MISP
Summary
by MITRE • 09/21/2026
MISP contains a DOM-based cross-site scripting (XSS) vulnerability in the contextual menu JavaScript component. The ContextualMenu class populates HTML <option> elements by assigning user-controllable values to the innerHTML property. Because innerHTML parses and renders HTML markup, any untrusted string supplied as the option text (value.text or value) is interpreted as live DOM content rather than plain text. An attacker who can influence the data rendered in the contextual menu can inject arbitrary HTML or JavaScript that executes in the victim's browser within the MISP application origin. This may allow session hijacking, data exfiltration, or unauthorized actions performed on behalf of the authenticated user.
Version affected: <2.5.47
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Analysis
by VulDB Data Team • 09/21/2026
The vulnerability identified as a DOM-based cross-site scripting flaw in the MISP platform stems from improper handling of untrusted input within its contextual menu JavaScript component. Specifically, the ContextualMenu class is designed to populate HTML option elements by directly assigning user-controllable values to the innerHTML property. This architectural decision creates a critical security gap because the innerHTML method does not treat assigned strings as plain text; instead, it parses and renders them as live DOM content. Consequently, any untrusted string supplied as the option text, whether derived from value.text or value parameters, is interpreted by the browser's rendering engine as executable HTML markup rather than static data. This behavior allows an attacker who can influence the data rendered in the contextual menu to inject arbitrary HTML or JavaScript payloads that will execute within the victim's browser context under the origin of the MISP application.
From a technical perspective, this vulnerability is classified under CWE-79, which covers Improper Neutralization of Input During Web Page Generation commonly known as Cross-site Scripting. The specific mechanism here aligns with DOM-based XSS patterns where the source of the data is within the client-side JavaScript and the sink is the innerHTML property assignment. Unlike stored or reflected XSS, this vulnerability relies on the dynamic manipulation of the Document Object Model by malicious scripts that have gained access to the application's context through manipulated input fields or API responses that are subsequently rendered in the menu structure. The lack of proper encoding or sanitization before DOM insertion means that special characters such as angle brackets and quotes are not escaped, allowing for the injection of script tags or event handlers like onerror or onload which trigger immediate execution upon rendering.
The operational impact of this vulnerability is severe due to its potential for session hijacking, data exfiltration, and unauthorized actions performed on behalf of authenticated users. Since the malicious code executes within the MISP application origin, it inherits all privileges associated with that domain, including access to cookies, local storage, and active sessions. An attacker could craft a payload that steals sensitive authentication tokens or extracts confidential threat intelligence data stored in memory or DOM elements. Furthermore, because MISP is often used by security professionals handling critical infrastructure information, the compromise of user accounts can lead to significant operational disruptions and potential leakage of high-value indicators of compromise. The attack vector typically requires social engineering or a compromised upstream system that feeds malicious data into the contextual menu inputs, leveraging the trust users place in the platform's interface elements.
Mitigation strategies must focus on preventing untrusted data from being interpreted as executable code within the DOM. Developers should replace direct innerHTML assignments with safer alternatives such as textContent for plain text insertion or use dedicated templating engines that automatically escape special characters. If HTML rendering is strictly necessary, a robust sanitization library compliant with OWASP guidelines should be employed to strip dangerous tags and attributes before assignment. Additionally, implementing Content Security Policy headers can provide an additional layer of defense by restricting the sources from which scripts can be loaded or executed, thereby mitigating the impact even if injection occurs. For users running affected versions prior to 2.5.47, immediate upgrading to a patched version is essential to close this security gap and protect against potential exploitation in production environments where sensitive threat intelligence data is managed.