Vulnerability-Lookup

CVE-2026-42599 (GCVE-0-2026-42599)

Vulnerability from cvelistv5 – Published: 2026-06-09 16:22 – Updated: 2026-06-09 18:39

Title

Cross-site scripting via spread attributes in Svelte SSR

Summary

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.

Severity

5.1 (Medium)


                        
                          CVSS:4.0/AV:N/AC:H/AT:P/PR:H/UI:N/VC:N/VI:N/VA:N/SC:H/SI:H/SA:N

SSVC

Exploitation: none Automatable: no Technical Impact: partial

CISA Coordinator (v2.0.3)

CWE

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

Assigner

GitHub_M

References

2 references

URL	Tags
https://github.com/sveltejs/svelte/security/advis…	x_refsource_CONFIRM
https://github.com/sveltejs/svelte/releases/tag/s…	x_refsource_MISC

Impacted products

1 product

Vendor	Product	Version
sveltejs	svelte	Affected: < 5.55.7

Show details on NVD website

JSON

To clipboard

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FKIE_CVE-2026-42599

Vulnerability from fkie_nvd - Published: 2026-06-09 17:17 - Updated: 2026-07-23 08:10

Severity

6.1 (Medium) - CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

Summary

References

	URL	Tags
	security-advisories@github.com	https://github.com/sveltejs/svelte/releases/tag/svelte%405.55.7	Release Notes
	security-advisories@github.com	https://github.com/sveltejs/svelte/security/advisories/GHSA-pr6f-5x2q-rwfp	Vendor Advisory

Impacted products

	Vendor	Product	Version
	svelte	svelte	*

JSON

To clipboard

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      "affectedData": [
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          "product": "svelte",
          "vendor": "sveltejs",
          "versions": [
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    },
    {
      "lang": "es",
      "value": "Svelte es un framework web orientado al rendimiento. Antes de la versi\u00f3n 5.55.7, al usar la sintaxis de propagaci\u00f3n (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 aplicaci\u00f3n 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 v\u00edctimas. Tenga en cuenta que esta vulnerabilidad solo se activa si el navegador del usuario tiene JavaScript habilitado, pero el mecanismo de hidrataci\u00f3n de Svelte no alcanza el elemento vulnerable antes de que se dispare el evento. Este problema ha sido parcheado en la versi\u00f3n 5.55.7."
    }
  ],
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  "lastModified": "2026-07-23T08:10:00.137",
  "metrics": {
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          "exploitMaturity": "NOT_DEFINED",
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          "modifiedAttackComplexity": "NOT_DEFINED",
          "modifiedAttackRequirements": "NOT_DEFINED",
          "modifiedAttackVector": "NOT_DEFINED",
          "modifiedPrivilegesRequired": "NOT_DEFINED",
          "modifiedSubAvailabilityImpact": "NOT_DEFINED",
          "modifiedSubConfidentialityImpact": "NOT_DEFINED",
          "modifiedSubIntegrityImpact": "NOT_DEFINED",
          "modifiedUserInteraction": "NOT_DEFINED",
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}

GHSA-PR6F-5X2Q-RWFP

Vulnerability from github – Published: 2026-05-14 20:19 – Updated: 2026-06-09 18:41

Summary

Svelte SSR vulnerable to cross-site scripting via spread attributes

Details

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 is similar to but different from CVE-2026-27121.

Severity

5.1 (Medium)


                  
                    CVSS:4.0/AV:N/AC:H/AT:P/PR:H/UI:N/VC:N/VI:N/VA:N/SC:H/SI:H/SA:N

Show details on source website

JSON

To clipboard

{
  "affected": [
    {
      "database_specific": {
        "last_known_affected_version_range": "\u003c= 5.55.6"
      },
      "package": {
        "ecosystem": "npm",
        "name": "svelte"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "5.55.7"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-42599"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-79"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-05-14T20:19:42Z",
    "nvd_published_at": "2026-06-09T17:17:07Z",
    "severity": "MODERATE"
  },
  "details": "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\u0027 browsers. Note that this vulnerability _only_ triggers if the user\u0027s browser has JavaScript enabled but Svelte\u0027s hydration mechanism does not reach the vulnerable element before the event fires.\n\nThis is similar to but different from [CVE-2026-27121](https://nvd.nist.gov/vuln/detail/CVE-2026-27121).",
  "id": "GHSA-pr6f-5x2q-rwfp",
  "modified": "2026-06-09T18:41:32Z",
  "published": "2026-05-14T20:19:42Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/sveltejs/svelte/security/advisories/GHSA-pr6f-5x2q-rwfp"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-27121"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-42599"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/sveltejs/svelte"
    },
    {
      "type": "WEB",
      "url": "https://github.com/sveltejs/svelte/releases/tag/svelte%405.55.7"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:4.0/AV:N/AC:H/AT:P/PR:H/UI:N/VC:N/VI:N/VA:N/SC:H/SI:H/SA:N",
      "type": "CVSS_V4"
    }
  ],
  "summary": "Svelte SSR vulnerable to cross-site scripting via spread attributes"
}

Sightings

Author	Source	Type	Date	Other

Nomenclature

Seen: The vulnerability was mentioned, discussed, or observed by the user.
Confirmed: The vulnerability has been validated from an analyst's perspective.
Published Proof of Concept: A public proof of concept is available for this vulnerability.
Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
Not confirmed: The user expressed doubt about the validity of the vulnerability.
Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

Detection rules are retrieved from Rulezet.

The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base model, served locally by ML-Gateway. They have not been verified by an analyst and are provided for guidance only.

Action not permitted

CVE-2026-42599 (GCVE-0-2026-42599)

FKIE_CVE-2026-42599

GHSA-PR6F-5X2Q-RWFP

Tags

Sightings

Nomenclature