CVE-2026-27121
Medium · 5.4CVSS
5.4
EPSS
0.3%
Published
Feb 20, 2026
CISA due date
—
The record
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.
Affected packages
| Ecosystem | Package | Introduced | Fixed |
|---|---|---|---|
| npm | svelte | 0 | 5.51.5 |
| Chainguard | langfuse-3-worker | 0 | 3.163.0-r0 |
| Chainguard | langfuse-fips-3-worker | 0 | 3.163.0-r0 |
| Wolfi | langfuse-3-worker | 0 | 3.163.0-r0 |
Related vulnerabilities
- GHSA-f7gr-6p89-r883 Svelte affected by cross-site scripting via spread attributes in Svelte SSR Same vulnerability
- CVE-2026-42567 Svelte is a performance oriented web framework. Also affects svelte
- CVE-2026-42599 Svelte is a performance oriented web framework. Also affects svelte
- CVE-2026-42573 Svelte is a performance oriented web framework. Also affects svelte
- GHSA-f3cj-j4f6-wq85 Svelte: SSR XSS via Insecure Promise Serialization in hydratable Also affects svelte
- GHSA-rcqx-6q8c-2c42 Svelte Vulnerable to XSS via DOM Clobbering of Internal Framework State Also affects svelte
- GHSA-9rmh-mm8f-r9h6 Svelte: ReDoS in `` Tag Validation Also affects svelte
- GHSA-pr6f-5x2q-rwfp Svelte SSR vulnerable to cross-site scripting via spread attributes Also affects svelte