CVE-2026-27902 PUBLISHED

Svelte Vulnerable to XSS via HTML Comment Injection in SSR Error Boundary Hydration Markers

Assigner: GitHub_M
Reserved: 24.02.2026 Published: 26.02.2026 Updated: 26.02.2026

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.

Metrics

CVSS 4.0

CVSS 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
CVSS Score: 5.3

Exploitability Metrics		Vulnerable System Impact Metrics		Subsequent System Impact Metrics
Attack Vector	Network	Confidentiality	Low	Confidentiality	High
Attack Complexity	High	Integrity	None	Integrity	High
Attack Requirements	Present	Availability	None	Availability	None
Privileges Required	None
User Interaction	Passive

CVSS 4.0

Product Status

Vendor	sveltejs
Product	svelte
Versions	Version >= 5.53.0, < 5.53.5 is affected

References

Problem Types

CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') CWE