CVE-2026-27121— Svelte affected by cross-site scripting via spread attributes in Svelte SSR
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I. Basic Information for CVE-2026-27121
Vulnerability Information
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Vulnerability Title
Svelte affected by cross-site scripting via spread attributes in Svelte SSR
Source: NVD (National Vulnerability Database)
Vulnerability Description
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.
Source: NVD (National Vulnerability Database)
CVSS Information
N/A
Source: NVD (National Vulnerability Database)
Vulnerability Type
在Web页面生成时对输入的转义处理不恰当(跨站脚本)
Source: NVD (National Vulnerability Database)
Vulnerability Title
Svelte 跨站脚本漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Svelte是Svelte开源的一种构建 Web 应用程序的新方法。 Svelte 5.51.5之前版本存在跨站脚本漏洞，该漏洞源于服务器端渲染期间使用扩展语法时包含事件处理程序属性，可能导致跨站脚本攻击。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)
Affected Products
II. Public POCs for CVE-2026-27121
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Same Patch Batch · sveltejs · 2026-02-20 · 5 CVEs total
| CVE-2026-27119 | Svelte affected by XSS in SSR `<option>` element | |
| CVE-2026-27125 | Svelte SSR attribute spreading includes inherited properties from prototype chain | |
| CVE-2026-27118 | Cache poisoning in @sveltejs/adapter-vercel | |
| CVE-2026-27122 | Svelte SSR does not validate dynamic element tag names in `<svelte:element>` |
IV. Related Vulnerabilities
Same product: svelte
- CVE-2026-27902
Svelte Vulnerable to XSS via HTML Comment Injection in SSR E - CVE-2026-27901
Svelte vulnerable to XSS during SSR with contenteditable `bi - CVE-2026-27125
Svelte SSR attribute spreading includes inherited properties - CVE-2026-27122
Svelte SSR does not validate dynamic element tag names in `< - CVE-2026-27119
Svelte affected by XSS in SSR `<option>` element
Same vendor: sveltejs
- CVE-2026-40074
SvelteKit's invalidated redirect in handle hook causes Denia - CVE-2026-40073
SvelteKit has a BODY_SIZE_LIMIT bypass in @sveltejs/adapter- - CVE-2026-30226
devalue has prototype pollution in devalue.parse and devalue - CVE-2026-27902
Svelte Vulnerable to XSS via HTML Comment Injection in SSR E - CVE-2026-27901
Svelte vulnerable to XSS during SSR with contenteditable `bi
Same weakness: CWE-79
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V. Comments for CVE-2026-27121
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