CVE-2026-27121: Svelte affected by cross-site scripting via spread attributes in Svelte SSR
svelte performance oriented web framework. Versions of svelte prior to 5.51.5 are vulnerable to cross-site scripting (XSS) during server-side rendering. When using spread syntax to render attributes from untrusted data, event handler properties are included in the rendered HTML output. If an application spreads user-controlled or external data as element attributes, an attacker can inject malicious event handlers that execute in victims' browsers. This vulnerability is fixed in 5.51.5.
Affected Software
Event History
Frequently Asked Questions
What is the severity of CVE-2026-27121?
CVE-2026-27121 has a medium severity rating due to its potential for cross-site scripting vulnerabilities.
How do I fix CVE-2026-27121?
To fix CVE-2026-27121, upgrade Svelte to version 5.51.5 or later.
What software is affected by CVE-2026-27121?
CVE-2026-27121 affects Svelte versions prior to 5.51.5.
What type of vulnerability is CVE-2026-27121?
CVE-2026-27121 is a cross-site scripting (XSS) vulnerability occurring during server-side rendering.
How does CVE-2026-27121 affect my application?
CVE-2026-27121 can expose your application to XSS attacks if untrusted data is rendered without proper sanitization.