CVE-2026-27122 PUBLISHED

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

Assigner: GitHub_M
Reserved: 17.02.2026 Published: 20.02.2026 Updated: 20.02.2026

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.

Metrics

CVSS 4.0

CVSS Vector: 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
CVSS Score: 5.1

Exploitability Metrics		Vulnerable System Impact Metrics		Subsequent System Impact Metrics
Attack Vector	Network	Confidentiality	Low	Confidentiality	High
Attack Complexity	High	Integrity	None	Integrity	High
Attack Requirements	Present	Availability	None	Availability	None
Privileges Required	High
User Interaction	None

CVSS 4.0

Product Status

Vendor	sveltejs
Product	svelte
Versions	Version < 5.51.5 is affected

References

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

Problem Types

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