GHSA-PR6F-5X2Q-RWFP

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



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Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

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.



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