CVE-2026-27121
Svelte affected by cross-site scripting via spread attributes in Svelte SSR
EPSS 0.01%
Description
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.
How to fix CVE-2026-27121
To remediate CVE-2026-27121, upgrade the affected package to a fixed version below.
- —upgrade to 5.51.5 or later
Is CVE-2026-27121 being exploited?
Low — EPSS is 0.0%, meaning exploitation activity has not been observed at scale.
Affected packages (1)
- from 0, < 5.51.5
CVSS scores
| Source | Version | Severity | Vector |
|---|---|---|---|
| osv | CVSS 4.0 | — | 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 |