GHSA-9RMH-MM8F-R9H6

Vulnerability from github – Published: 2026-05-14 20:29 – Updated: 2026-06-09 18:41
VLAI
Summary
Svelte: ReDoS in `<svelte:element>` Tag Validation
Details

An internal regex in the Svelte runtime can take exponential time to test in <svelte:element this={tag}></svelte:element>. You are only vulnerable to this if you allow tags of unconstrained length. If your application only allows a predetermined list of tags or trims their length before passing them to svelte:element, you are safe.

Severity
5.9 (Medium)
CVSS:4.0/AV:N/AC:H/AT:P/PR:H/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/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": "5.51.5"
            },
            {
              "fixed": "5.55.7"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-42567"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-1333"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-05-14T20:29:05Z",
    "nvd_published_at": "2026-06-09T17:17:07Z",
    "severity": "MODERATE"
  },
  "details": "An internal regex in the Svelte runtime can take exponential time to test in `\u003csvelte:element this={tag}\u003e\u003c/svelte:element\u003e`. You are only vulnerable to this if you allow tags of unconstrained length. If your application only allows a predetermined list of tags or trims their length before passing them to `svelte:element`, you are safe.",
  "id": "GHSA-9rmh-mm8f-r9h6",
  "modified": "2026-06-09T18:41:19Z",
  "published": "2026-05-14T20:29:05Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/sveltejs/svelte/security/advisories/GHSA-9rmh-mm8f-r9h6"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-42567"
    },
    {
      "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:H/SC:N/SI:N/SA:N",
      "type": "CVSS_V4"
    }
  ],
  "summary": "Svelte: ReDoS in `\u003csvelte:element\u003e` Tag Validation"
}


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