CVE-2026-27122

Svelte SSR does not validate dynamic element tag names in `<svelte:element>`

State: Published
Severity: 5.1 Medium
Published: Feb 20, 2026
Updated: Feb 23, 2026
Reserved: Feb 17, 2026

Description

svelte performance oriented web framework. Prior to 5.51.5, when using <svelte:element this={tag}> in server-side rendering, the provided tag name is not validated or sanitized before being emitted into the HTML output. If the tag string contains unexpected characters, it can result in HTML injection in the SSR output. Client-side rendering is not affected. This vulnerability is fixed in 5.51.5.

Scores

CVSS	Score	Vector	Source
4.0	5.1 Medium	CVSS:4.0/AV:N/AC:H/AT:P/PR:H/UI:N/VC:L/VI:N/VA:N/SC:H/SI:H/SA:N	GitHub_M

Weaknesses

CWE-79 Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')

Affected Products

Product	Versions
sveltesveltejs	< 5.51.5Affected

References

https://github.com/sveltejs/svelte/security/advisories/GHSA-m56q-vw4c-c2cp

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