What is CVE-2026-27902?

CVE-2026-27902 is a medium-severity vulnerability in Svelte, classified under Cross-site Scripting. CVSS score: 5.4/10. Published 2026-02-26.

How severe is CVE-2026-27902?

Medium severity. CVSS v3 base score is 5.4 out of 10.

XSS in Svelte

CVE-2026-27902

Svelte performance oriented web framework. Prior to version 5.53.5, errors from `transformError` were not correctly escaped prior to being embedded in the HTML output, causing potential HTML injection and XSS if attacker-controlled content is returned from `transformError`. Version 5.53.5 fixes the issue.

Vulnerability class: XSS (Cross-Site Scripting)

Published 2026-02-26 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 5.4 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:N.

EPSS exploit prediction

EPSS: 0.004 (30.3th percentile), scored 2026-09-29.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 30th percentile — 30.3% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.002 · newest: 0.004 · change: +0.002

Affected products

Svelte
Sveltejs Svelte — versions >= 5.53.0, < 5.53.5

Weakness classification (CWE)

CWE-79 — Cross-site Scripting

References

github.com/sveltejs/svelte/security/advisories/GHSA-qgvg-pr8v-6rr3 (Vendor Advisory)
github.com/sveltejs/svelte/commit/0298e979371bb583855c9810db79a70a551d22b9 (Patch)
github.com/sveltejs/svelte/releases/tag/svelte@5.53.5 (Release Notes)

Frequently asked questions

What is CVE-2026-27902?: CVE-2026-27902 is a medium-severity vulnerability in Svelte, classified under Cross-site Scripting. CVSS score: 5.4/10. Published 2026-02-26.
How severe is CVE-2026-27902?: Medium severity. CVSS v3 base score is 5.4 out of 10.