Vulnerability · Published Feb 26, 2026 · Assigned by GitHub_M

CVE-2026-27902Svelte Vulnerable to XSS via HTML Comment Injection in SSR Error Boundary Hydration Markers

Medium 5.3

In plain English

A medium-severity cross-site scripting in svelte from sveltejs. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.3% (higher than 20% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 4.0)5.3Medium

Exploit odds (30 days)0.3%top 80.4% of all CVEs

Exploited in the wildNo reportsCISA SSVC: none

Attack toolingNoneno public tooling known

Official description

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.

Affected packages & fixed versions

Ecosystem	Package	Fixed in	Advisory
npm	svelte	5.53.5	GHSA-qgvg-pr8v-6rr3

Affected products (as reported)

Vendor	Product	Versions
sveltejs	svelte	>= 5.53.0, < 5.53.5

Weakness: CWE-79 · Vector: CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:P/VC:L/VI:N/VA:N/SC:H/SI:H/SA:N

References

https://github.com/sveltejs/svelte/security/advisories/GHSA-qgvg-pr8v-6rr3 x_refsource_CONFIRM
https://github.com/sveltejs/svelte/commit/0298e979371bb583855c9810db79a70a551d22b9 x_refsource_MISC
https://github.com/sveltejs/svelte/releases/tag/svelte%405.53.5 x_refsource_MISC