CVE-2026-27122CWE-79

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

Medium · published February 20, 2026

CVSS v4.0
5.1
EPSS
0%
Percentile
16.0
In the wild
Unconfirmed
What it is

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.

The record
Technical detail
CVSS v4.0
5.1 · MEDIUM
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
EPSS
0.00254 · 16.0th percentile
Weakness
CWE-79 · Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
Published
2026-02-20T22:28Z
EPSS history
Timeline
  • 20 FEB 22:28Z
    Svelte SSR does not validate dynamic element tag names in `<svelte:element>`
    cvelistv5