CVE-2026-42599
Cross-site scripting via spread attributes in Svelte SSR
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.
INFO
Published Date :
June 9, 2026, 5:17 p.m.
Last Modified :
July 23, 2026, 8:10 a.m.
Remotely Exploit :
Yes !
Source :
[email protected]
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS | 134c704f-9b21-4f2e-91b3-4a467353bcc0 | |||||
| CVSS 3.1 | MEDIUM | [email protected] | ||||
| CVSS 4.0 | MEDIUM | [email protected] |
Solution
- Update Svelte to version 5.55.7 or newer.
- Avoid spreading untrusted data as HTML attributes.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2026-42599.
| URL | Resource |
|---|---|
| https://github.com/sveltejs/svelte/releases/tag/svelte%405.55.7 | Release Notes |
| https://github.com/sveltejs/svelte/security/advisories/GHSA-pr6f-5x2q-rwfp | Vendor Advisory |
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-42599 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2026-42599
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2026-42599 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2026-42599 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
-
CVE Translated by [email protected]
Jul. 23, 2026
Action Type Old Value New Value Added Translation Title: svelte de sveltejs, Description: Svelte es un framework web orientado al rendimiento. Antes de la versión 5.55.7, al usar la sintaxis de propagación (spread syntax) para renderizar atributos de datos no confiables, las propiedades de los gestores de eventos se incluyen en la salida HTML renderizada. Si una aplicación propaga datos controlados por el usuario o externos como atributos de elementos, un atacante puede inyectar gestores de eventos maliciosos que se ejecutan en los navegadores de las víctimas. Tenga en cuenta que esta vulnerabilidad solo se activa si el navegador del usuario tiene JavaScript habilitado, pero el mecanismo de hidratación de Svelte no alcanza el elemento vulnerable antes de que se dispare el evento. Este problema ha sido parcheado en la versión 5.55.7. -
CVE Modified by [email protected]
Jun. 17, 2026
Action Type Old Value New Value Added Affected [{'vendor': 'sveltejs', 'product': 'svelte', 'versions': [{'status': 'affected', 'version': '< 5.55.7'}]}] -
CVE Modified by 134c704f-9b21-4f2e-91b3-4a467353bcc0
Jun. 17, 2026
Action Type Old Value New Value Added SSVC {'id': 'CVE-2026-42599', 'role': 'CISA Coordinator', 'options': [{'exploitation': 'none'}, {'automatable': 'no'}, {'technicalImpact': 'partial'}], 'version': '2.0.3', 'timestamp': '2026-06-09T18:28:29.530383Z'} -
Initial Analysis by [email protected]
Jun. 11, 2026
Action Type Old Value New Value Added CVSS V3.1 AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N Added CPE Configuration OR *cpe:2.3:a:svelte:svelte:*:*:*:*:*:node.js:*:* versions up to (excluding) 5.55.7 Added Reference Type GitHub, Inc.: https://github.com/sveltejs/svelte/releases/tag/svelte%405.55.7 Types: Release Notes Added Reference Type GitHub, Inc.: https://github.com/sveltejs/svelte/security/advisories/GHSA-pr6f-5x2q-rwfp Types: Vendor Advisory -
New CVE Received by [email protected]
Jun. 09, 2026
Action Type Old Value New Value Added 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. Added CVSS V4.0 AV:N/AC:H/AT:P/PR:H/UI:N/VC:N/VI:N/VA:N/SC:H/SI:H/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X Added CWE CWE-79 Added Reference https://github.com/sveltejs/svelte/releases/tag/svelte%405.55.7 Added Reference https://github.com/sveltejs/svelte/security/advisories/GHSA-pr6f-5x2q-rwfp