CVE-2026-42599 Details
Description
Svelte is a performance oriented web framework. Prior to version 5.55.7, 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. Note that this vulnerability only triggers if the user's browser has JavaScript enabled but Svelte's hydration mechanism does not reach the vulnerable element before the event fires. This issue has been patched in version 5.55.7.
A cross-site scripting vulnerability has been identified in Svelte versions prior to 5.55.7. When spread syntax is used to render attributes from untrusted data, event handler properties can be inadvertently included in the HTML output. This allows attackers to inject malicious event handlers that execute in the context of the victim's browser. The issue arises only if JavaScript is enabled and Svelte's hydration process does not reach the affected element before the event is triggered.
Users can upgrade to Svelte version 5.55.7 or later to address this vulnerability.
Metrics
CVSS 4.0 Severity and Vector Strings:
CVSS 3.x Severity and Vector Strings:
No data available for CVSS Version 2.0 on this CVE.
CISA-ADP
Assessed Jun 9, 2026References to Advisories, Solutions, and Tools
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| URL | Source(s) | Tag(s) |
|---|---|---|
| https://github.com/sveltejs/svelte/releases/tag/svelte%405.55.7 | [email protected] | Release Notes |
| https://github.com/sveltejs/svelte/security/advisories/GHSA-pr6f-5x2q-rwfp | [email protected] | Vendor Advisory |
Weakness Enumeration
| CWE-ID | CWE Name | Source |
|---|---|---|
| CWE-79 | Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') | [email protected] |
Affected Products
| Product | Versions |
|---|---|
| svelte svelte | < 5.55.7 |
CPE
Remediation
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Change History
5 change records found show changes
| Date | Action | Recorded By |
|---|---|---|
| Jul 23, 2026 | CVE Translated | [email protected] |
| Jun 17, 2026 | CVE Modified | [email protected] |
| Jun 17, 2026 | CVE Modified | CISA-ADP |
| Jun 11, 2026 | Initial Analysis | [email protected] |
| Jun 9, 2026 | New CVE Received | [email protected] |