CVE-2026-27121
Cross-Site Scripting in Svelte SSR via Attribute Spread
Publication date: 2026-02-20
Last updated on: 2026-02-23
Assigner: GitHub, Inc.
Description
Description
CVSS Scores
EPSS Scores
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Meta Information
Affected Vendors & Products
| Vendor | Product | Version / Range |
|---|---|---|
| svelte | svelte | to 5.51.5 (exc) |
Helpful Resources
Exploitability
| CWE ID | Description |
|---|---|
| CWE-79 | The product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users. |
Attack-Flow Graph
AI Powered Q&A
Can you explain this vulnerability to me?
This vulnerability affects versions of the Svelte web framework prior to 5.51.5. It is a cross-site scripting (XSS) issue that occurs during server-side rendering when using spread syntax to render attributes from untrusted data. Specifically, event handler properties from user-controlled or external data are included in the rendered HTML output, allowing an attacker to inject malicious event handlers that execute in the browsers of users viewing the affected application.
How can this vulnerability impact me? :
The vulnerability can allow attackers to execute malicious scripts in the browsers of users interacting with the affected application. This can lead to unauthorized actions, data theft, session hijacking, or other malicious activities performed on behalf of the victim without their consent.
How does this vulnerability affect compliance with common standards and regulations (like GDPR, HIPAA)?:
I don't know
How can this vulnerability be detected on my network or system? Can you suggest some commands?
I don't know
What immediate steps should I take to mitigate this vulnerability?
To mitigate this vulnerability, upgrade the svelte framework to version 5.51.5 or later, where the issue is fixed.
Additionally, avoid using spread syntax to render attributes from untrusted or user-controlled data, especially event handler properties, to prevent injection of malicious event handlers.