Executive Summary

CVE-2026-42573 is a DOM clobbering vulnerability in the Svelte framework that affects versions prior to 5.55.7.

This vulnerability occurs when attribute spreading is used on a form element along with dynamic or user-controllable values for the name attribute on input or button elements within that form.

An attacker can exploit this to manipulate the internal framework state, potentially leading to cross-site scripting (XSS) attacks by executing malicious scripts.

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Impact Analysis

This vulnerability can impact you by allowing attackers to execute unauthorized scripts within your application, leading to cross-site scripting (XSS) attacks.

Such attacks can compromise the confidentiality and integrity of your systems by enabling unauthorized data access and modification.

The vulnerability requires low privileges and no user interaction but has high attack complexity and present attack requirements.

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Detection Guidance

This vulnerability occurs in Svelte versions prior to 5.55.7 when attribute spreading is used on form elements along with dynamic or user-controllable values for the name attribute on input or button elements within that form.

Detection involves identifying if your application uses a vulnerable version of Svelte and if it uses attribute spreading on form elements with dynamic name attributes on inputs or buttons.

Since this is a framework-level vulnerability related to DOM clobbering and XSS, network detection commands are not directly applicable.

To detect vulnerable versions, you can check the installed Svelte version in your project by running:

• npm list svelte

To scan your codebase for usage patterns that might be vulnerable, you can search for attribute spreading on form elements and dynamic name attributes using commands like:

• grep -r "<form" ./src
• grep -r "name={" ./src

Manual code review focusing on these patterns is recommended to identify potential exploit points.

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Mitigation Strategies

The primary mitigation step is to upgrade Svelte to version 5.55.7 or later, where this vulnerability has been patched.

Avoid using attribute spreading on form elements combined with dynamic or user-controllable values for the name attribute on input or button elements until the upgrade is applied.

Review your codebase for any such usage patterns and refactor them to use static or sanitized values.

Apply general security best practices such as sanitizing user inputs and implementing Content Security Policy (CSP) headers to reduce the impact of potential XSS attacks.

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Compliance Impact

The vulnerability in Svelte prior to version 5.55.7 allows for DOM clobbering that can lead to cross-site scripting (XSS) attacks. Such attacks can compromise the confidentiality and integrity of data by enabling unauthorized data access and modification.

Since regulations like GDPR and HIPAA require protection of personal and sensitive data against unauthorized access and breaches, this vulnerability could negatively impact compliance by exposing systems to potential data breaches through XSS attacks.

Therefore, if an application using vulnerable versions of Svelte processes regulated data, it may be at increased risk of non-compliance with these standards until the vulnerability is patched.

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