CVE-2026-106159 in Kendo UI for jQuery
Summary
by MITRE • 10/15/2026
In Progress® Kendo® UI for jQuery versions starting with 2022.3.1109 and prior to 2026.3.1015, ToolBar ButtonGroup button URLs are concatenated into an unquoted href attribute after URL sanitization. An attacker who can control a button URL can supply an otherwise allowed HTTPS URL containing whitespace and additional attributes, including an event handler, and execute JavaScript in a user's browser when the affected button is interacted with. Successful exploitation can compromise the confidentiality and integrity of data accessible to the affected application. This issue is fixed in version 2026.3.1015.
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Analysis
by VulDB Data Team • 10/15/2026
The vulnerability identified in Progress Kendo UI for jQuery, specifically affecting versions from 2022.3.1109 up to but not including 2026.3.1015, represents a significant client-side security flaw rooted in improper output encoding and URL sanitization logic. This issue is classified under CWE-79, which denotes Cross-site Scripting (XSS), specifically reflecting an instance of reflected or stored XSS depending on how the button URLs are sourced within the application architecture. The core technical failure occurs during the rendering phase where ToolBar ButtonGroup buttons generate their hyperlinks. Instead of properly quoting the href attribute value after sanitization, the library concatenates the URL directly into the HTML markup without ensuring it is enclosed in quotes. This deviation from standard HTML parsing rules creates a context where an attacker can inject malicious payloads that break out of the intended attribute scope and execute arbitrary JavaScript code within the victim's browser environment.
The operational mechanism of this exploit relies on the specific behavior of web browsers when encountering unquoted attributes. When a button URL contains whitespace, such as a space character followed by additional HTML attributes like an event handler (e.g., onclick or onerror), the browser interprets these additions not as part of the URL string but as new HTML attributes applied to the anchor element itself. For instance, if an attacker supplies a URL that includes a space and then appends an attribute such as onload=alert(1), the resulting HTML might resemble <a href=https://example.com onload=alert(1)>. Because the href is unquoted, the browser parses this structure correctly enough to attach the event handler to the link. Consequently, when a user interacts with the affected button by clicking it or hovering over it depending on the specific payload used, the malicious JavaScript executes in the context of the vulnerable application's domain.
The impact of successful exploitation extends beyond mere script execution and directly compromises the confidentiality and integrity of data accessible to the end-user. Since the injected scripts run with the same privileges as legitimate application code, an attacker can access sensitive cookies, local storage items, or session tokens associated with the user’s current login state. This capability allows for account takeover scenarios where the attacker impersonates a valid user, potentially leading to unauthorized actions such as data exfiltration, modification of critical records, or further propagation within the organization if other services are accessible from that domain. The integrity aspect is compromised because the application's behavior can be manipulated through DOM manipulation performed by the injected script, altering UI elements or redirecting users to phishing sites while maintaining the appearance of legitimacy.
From a threat intelligence perspective, this vulnerability aligns with MITRE ATT&CK technique T1059.007, which covers JavaScript execution in web browsers as part of Command and Control or Initial Access phases depending on the delivery method. The lack of proper output encoding is a classic example of insufficient validation during data rendering, highlighting the importance of strict adherence to OWASP guidelines for preventing XSS attacks. Developers must ensure that all dynamic content inserted into HTML attributes is properly encoded and quoted to prevent attribute injection vectors. In this specific case, the fix implemented in version 2026.3.1015 addresses the root cause by ensuring that href values are consistently wrapped in quotes regardless of their content, thereby neutralizing the ability to inject additional HTML attributes via whitespace separation.
Mitigation strategies for organizations still running affected versions include immediate upgrading to version 2026.3.1015 or later as recommended by Progress Software. For environments where an upgrade is not immediately feasible, a temporary workaround involves implementing custom sanitization logic that strictly validates URL inputs and rejects any URLs containing whitespace characters before they are passed to the Kendo UI components. Additionally, deploying Content Security Policy headers can help mitigate the impact of successful exploitation by restricting the sources from which scripts can be executed, although this is not a substitute for fixing the underlying vulnerability in the library code itself. Regular security audits focusing on input validation and output encoding practices across all third-party libraries are essential to prevent similar vulnerabilities from being introduced or exploited in web applications.