Vulnerability-Lookup

GHSA-9RMH-MM8F-R9H6

Vulnerability from github – Published: 2026-05-14 20:29 – Updated: 2026-06-09 18:41

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"
}

CVE-2026-42567 (GCVE-0-2026-42567)

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

Title

Svelte: ReDoS in `<svelte:element>` Tag Validation

Summary

Svelte is a performance oriented web framework. From version 5.51.5 to before version 5.55.7, an internal regex in the Svelte runtime can take exponential time to test in <svelte:element this={tag}></svelte:element>. This issue has been patched in version 5.55.7.

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

SSVC

Exploitation: none Automatable: no Technical Impact: partial

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2026-06-09 18:09 UTC

CWE

CWE-1333 - Inefficient Regular Expression Complexity

Assigner

GitHub_M CNA under the mitre root

CNA scorecard C 72/100 over 7642 records in the last 180 days details

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: >= 5.51.5, < 5.55.7

Show details on NVD website

JSON

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{
  "containers": {
    "adp": [
      {
        "metrics": [
          {
            "other": {
              "content": {
                "id": "CVE-2026-42567",
                "options": [
                  {
                    "Exploitation": "none"
                  },
                  {
                    "Automatable": "no"
                  },
                  {
                    "Technical Impact": "partial"
                  }
                ],
                "role": "CISA Coordinator",
                "timestamp": "2026-06-09T18:09:08.059769Z",
                "version": "2.0.3"
              },
              "type": "ssvc"
            }
          }
        ],
        "providerMetadata": {
          "dateUpdated": "2026-06-09T18:09:26.356Z",
          "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
          "shortName": "CISA-ADP"
        },
        "title": "CISA ADP Vulnrichment"
      }
    ],
    "cna": {
      "affected": [
        {
          "product": "svelte",
          "vendor": "sveltejs",
          "versions": [
            {
              "status": "affected",
              "version": "\u003e= 5.51.5, \u003c 5.55.7"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "Svelte is a performance oriented web framework. From version 5.51.5 to before version 5.55.7, an internal regex in the Svelte runtime can take exponential time to test in \u003csvelte:element this={tag}\u003e\u003c/svelte:element\u003e. This issue has been patched in version 5.55.7."
        }
      ],
      "metrics": [
        {
          "cvssV4_0": {
            "attackComplexity": "HIGH",
            "attackRequirements": "PRESENT",
            "attackVector": "NETWORK",
            "baseScore": 5.9,
            "baseSeverity": "MEDIUM",
            "privilegesRequired": "HIGH",
            "subAvailabilityImpact": "NONE",
            "subConfidentialityImpact": "NONE",
            "subIntegrityImpact": "NONE",
            "userInteraction": "NONE",
            "vectorString": "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",
            "version": "4.0",
            "vulnAvailabilityImpact": "HIGH",
            "vulnConfidentialityImpact": "NONE",
            "vulnIntegrityImpact": "NONE"
          }
        }
      ],
      "problemTypes": [
        {
          "descriptions": [
            {
              "cweId": "CWE-1333",
              "description": "CWE-1333: Inefficient Regular Expression Complexity",
              "lang": "en",
              "type": "CWE"
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-06-09T16:22:22.703Z",
        "orgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
        "shortName": "GitHub_M"
      },
      "references": [
        {
          "name": "https://github.com/sveltejs/svelte/security/advisories/GHSA-9rmh-mm8f-r9h6",
          "tags": [
            "x_refsource_CONFIRM"
          ],
          "url": "https://github.com/sveltejs/svelte/security/advisories/GHSA-9rmh-mm8f-r9h6"
        },
        {
          "name": "https://github.com/sveltejs/svelte/releases/tag/svelte%405.55.7",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/sveltejs/svelte/releases/tag/svelte%405.55.7"
        }
      ],
      "source": {
        "advisory": "GHSA-9rmh-mm8f-r9h6",
        "discovery": "UNKNOWN"
      },
      "title": "Svelte: ReDoS in `\u003csvelte:element\u003e` Tag Validation"
    }
  },
  "cveMetadata": {
    "assignerOrgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
    "assignerShortName": "GitHub_M",
    "cveId": "CVE-2026-42567",
    "datePublished": "2026-06-09T16:22:22.703Z",
    "dateReserved": "2026-04-28T17:26:12.084Z",
    "dateUpdated": "2026-06-09T18:09:26.356Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}

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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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.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
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