Vulnerability-Lookup

CVE-2026-66062 (GCVE-0-2026-66062)

Vulnerability from cvelistv5 – Published: 2026-08-07 16:49 – Updated: 2026-08-07 21:02

Title

SvelteKit: ReDoS (O(n^2)) in content negotiation — unauthenticated DoS via the Accept header

Summary

SvelteKit is a framework for rapidly developing robust, performant web applications using Svelte. Prior to 2.70.2, the content negotiation header parser used by SvelteKit's request handling (for headers such as Accept) uses a regular expression vulnerable to quadratic backtracking, so a maliciously crafted header value can cause excessive CPU consumption and degrade or deny service. Version 2.70.2 fixes the issue.

Severity

5.3 (Medium)


                        
                          CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

SSVC

Exploitation: none Automatable: yes Technical Impact: partial

CISA Coordinator (v2.0.3)

CWE

CWE-1333 - Inefficient Regular Expression Complexity

Assigner

GitHub_M

References

3 references

URL	Tags
https://github.com/sveltejs/kit/security/advisori…	x_refsource_CONFIRM
https://github.com/sveltejs/kit/commit/82712fc02c…	x_refsource_MISC
https://github.com/sveltejs/kit/releases/tag/@sve…	x_refsource_MISC

Impacted products

1 product

Vendor	Product	Version
sveltejs	kit	Affected: < 2.70.2

Show details on NVD website

JSON

To clipboard

{
  "containers": {
    "adp": [
      {
        "metrics": [
          {
            "other": {
              "content": {
                "id": "CVE-2026-66062",
                "options": [
                  {
                    "Exploitation": "none"
                  },
                  {
                    "Automatable": "yes"
                  },
                  {
                    "Technical Impact": "partial"
                  }
                ],
                "role": "CISA Coordinator",
                "timestamp": "2026-08-07T20:58:04.458547Z",
                "version": "2.0.3"
              },
              "type": "ssvc"
            }
          }
        ],
        "providerMetadata": {
          "dateUpdated": "2026-08-07T21:02:12.997Z",
          "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
          "shortName": "CISA-ADP"
        },
        "title": "CISA ADP Vulnrichment"
      }
    ],
    "cna": {
      "affected": [
        {
          "product": "kit",
          "vendor": "sveltejs",
          "versions": [
            {
              "status": "affected",
              "version": "\u003c 2.70.2"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "SvelteKit is a framework for rapidly developing robust, performant web applications using Svelte. Prior to 2.70.2, the content negotiation header parser used by SvelteKit\u0027s request handling (for headers such as Accept) uses a regular expression vulnerable to quadratic backtracking, so a maliciously crafted header value can cause excessive CPU consumption and degrade or deny service. Version 2.70.2 fixes the issue."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "attackComplexity": "LOW",
            "attackVector": "NETWORK",
            "availabilityImpact": "LOW",
            "baseScore": 5.3,
            "baseSeverity": "MEDIUM",
            "confidentialityImpact": "NONE",
            "integrityImpact": "NONE",
            "privilegesRequired": "NONE",
            "scope": "UNCHANGED",
            "userInteraction": "NONE",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L",
            "version": "3.1"
          }
        }
      ],
      "problemTypes": [
        {
          "descriptions": [
            {
              "cweId": "CWE-1333",
              "description": "CWE-1333: Inefficient Regular Expression Complexity",
              "lang": "en",
              "type": "CWE"
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-07T16:49:43.853Z",
        "orgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
        "shortName": "GitHub_M"
      },
      "references": [
        {
          "name": "https://github.com/sveltejs/kit/security/advisories/GHSA-29g2-3rmr-qm68",
          "tags": [
            "x_refsource_CONFIRM"
          ],
          "url": "https://github.com/sveltejs/kit/security/advisories/GHSA-29g2-3rmr-qm68"
        },
        {
          "name": "https://github.com/sveltejs/kit/commit/82712fc02c24b1dcf5b25d7a52129cd8455f04f5",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/sveltejs/kit/commit/82712fc02c24b1dcf5b25d7a52129cd8455f04f5"
        },
        {
          "name": "https://github.com/sveltejs/kit/releases/tag/@sveltejs/kit@2.70.2",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/sveltejs/kit/releases/tag/@sveltejs/kit@2.70.2"
        }
      ],
      "source": {
        "advisory": "GHSA-29g2-3rmr-qm68",
        "discovery": "UNKNOWN"
      },
      "title": "SvelteKit: ReDoS (O(n^2)) in content negotiation \u2014 unauthenticated DoS via the Accept header"
    }
  },
  "cveMetadata": {
    "assignerOrgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
    "assignerShortName": "GitHub_M",
    "cveId": "CVE-2026-66062",
    "datePublished": "2026-08-07T16:49:43.853Z",
    "dateReserved": "2026-07-23T23:25:28.896Z",
    "dateUpdated": "2026-08-07T21:02:12.997Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2",
  "vulnerability-lookup:meta": {
    "nvd": "{\"cve\":{\"id\":\"CVE-2026-66062\",\"sourceIdentifier\":\"security-advisories@github.com\",\"published\":\"2026-08-07T17:17:06.340\",\"lastModified\":\"2026-08-07T22:16:59.637\",\"vulnStatus\":\"Received\",\"cveTags\":[],\"descriptions\":[{\"lang\":\"en\",\"value\":\"SvelteKit is a framework for rapidly developing robust, performant web applications using Svelte. Prior to 2.70.2, the content negotiation header parser used by SvelteKit\u0027s request handling (for headers such as Accept) uses a regular expression vulnerable to quadratic backtracking, so a maliciously crafted header value can cause excessive CPU consumption and degrade or deny service. Version 2.70.2 fixes the issue.\"}],\"affected\":[{\"source\":\"security-advisories@github.com\",\"affectedData\":[{\"vendor\":\"sveltejs\",\"product\":\"kit\",\"versions\":[{\"version\":\"\u003c 2.70.2\",\"status\":\"affected\"}]}]}],\"metrics\":{\"cvssMetricV31\":[{\"source\":\"security-advisories@github.com\",\"type\":\"Secondary\",\"cvssData\":{\"version\":\"3.1\",\"vectorString\":\"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L\",\"baseScore\":5.3,\"baseSeverity\":\"MEDIUM\",\"attackVector\":\"NETWORK\",\"attackComplexity\":\"LOW\",\"privilegesRequired\":\"NONE\",\"userInteraction\":\"NONE\",\"scope\":\"UNCHANGED\",\"confidentialityImpact\":\"NONE\",\"integrityImpact\":\"NONE\",\"availabilityImpact\":\"LOW\"},\"exploitabilityScore\":3.9,\"impactScore\":1.4}],\"ssvcV203\":[{\"source\":\"134c704f-9b21-4f2e-91b3-4a467353bcc0\",\"ssvcData\":{\"timestamp\":\"2026-08-07T20:58:04.458547Z\",\"id\":\"CVE-2026-66062\",\"options\":[{\"exploitation\":\"none\"},{\"automatable\":\"yes\"},{\"technicalImpact\":\"partial\"}],\"role\":\"CISA Coordinator\",\"version\":\"2.0.3\"}}]},\"weaknesses\":[{\"source\":\"security-advisories@github.com\",\"type\":\"Secondary\",\"description\":[{\"lang\":\"en\",\"value\":\"CWE-1333\"}]}],\"references\":[{\"url\":\"https://github.com/sveltejs/kit/commit/82712fc02c24b1dcf5b25d7a52129cd8455f04f5\",\"source\":\"security-advisories@github.com\"},{\"url\":\"https://github.com/sveltejs/kit/releases/tag/@sveltejs/kit@2.70.2\",\"source\":\"security-advisories@github.com\"},{\"url\":\"https://github.com/sveltejs/kit/security/advisories/GHSA-29g2-3rmr-qm68\",\"source\":\"security-advisories@github.com\"}]}}",
    "vulnrichment": {
      "containers": "{\"adp\": [{\"title\": \"CISA ADP Vulnrichment\", \"metrics\": [{\"other\": {\"type\": \"ssvc\", \"content\": {\"id\": \"CVE-2026-66062\", \"role\": \"CISA Coordinator\", \"options\": [{\"Exploitation\": \"none\"}, {\"Automatable\": \"yes\"}, {\"Technical Impact\": \"partial\"}], \"version\": \"2.0.3\", \"timestamp\": \"2026-08-07T20:58:04.458547Z\"}}}], \"providerMetadata\": {\"orgId\": \"134c704f-9b21-4f2e-91b3-4a467353bcc0\", \"shortName\": \"CISA-ADP\", \"dateUpdated\": \"2026-08-07T20:58:44.242Z\"}}], \"cna\": {\"title\": \"SvelteKit: ReDoS (O(n^2)) in content negotiation \\u2014 unauthenticated DoS via the Accept header\", \"source\": {\"advisory\": \"GHSA-29g2-3rmr-qm68\", \"discovery\": \"UNKNOWN\"}, \"metrics\": [{\"cvssV3_1\": {\"scope\": \"UNCHANGED\", \"version\": \"3.1\", \"baseScore\": 5.3, \"attackVector\": \"NETWORK\", \"baseSeverity\": \"MEDIUM\", \"vectorString\": \"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L\", \"integrityImpact\": \"NONE\", \"userInteraction\": \"NONE\", \"attackComplexity\": \"LOW\", \"availabilityImpact\": \"LOW\", \"privilegesRequired\": \"NONE\", \"confidentialityImpact\": \"NONE\"}}], \"affected\": [{\"vendor\": \"sveltejs\", \"product\": \"kit\", \"versions\": [{\"status\": \"affected\", \"version\": \"\u003c 2.70.2\"}]}], \"references\": [{\"url\": \"https://github.com/sveltejs/kit/security/advisories/GHSA-29g2-3rmr-qm68\", \"name\": \"https://github.com/sveltejs/kit/security/advisories/GHSA-29g2-3rmr-qm68\", \"tags\": [\"x_refsource_CONFIRM\"]}, {\"url\": \"https://github.com/sveltejs/kit/commit/82712fc02c24b1dcf5b25d7a52129cd8455f04f5\", \"name\": \"https://github.com/sveltejs/kit/commit/82712fc02c24b1dcf5b25d7a52129cd8455f04f5\", \"tags\": [\"x_refsource_MISC\"]}, {\"url\": \"https://github.com/sveltejs/kit/releases/tag/@sveltejs/kit@2.70.2\", \"name\": \"https://github.com/sveltejs/kit/releases/tag/@sveltejs/kit@2.70.2\", \"tags\": [\"x_refsource_MISC\"]}], \"descriptions\": [{\"lang\": \"en\", \"value\": \"SvelteKit is a framework for rapidly developing robust, performant web applications using Svelte. Prior to 2.70.2, the content negotiation header parser used by SvelteKit\u0027s request handling (for headers such as Accept) uses a regular expression vulnerable to quadratic backtracking, so a maliciously crafted header value can cause excessive CPU consumption and degrade or deny service. Version 2.70.2 fixes the issue.\"}], \"problemTypes\": [{\"descriptions\": [{\"lang\": \"en\", \"type\": \"CWE\", \"cweId\": \"CWE-1333\", \"description\": \"CWE-1333: Inefficient Regular Expression Complexity\"}]}], \"providerMetadata\": {\"orgId\": \"a0819718-46f1-4df5-94e2-005712e83aaa\", \"shortName\": \"GitHub_M\", \"dateUpdated\": \"2026-08-07T16:49:43.853Z\"}}}",
      "cveMetadata": "{\"cveId\": \"CVE-2026-66062\", \"state\": \"PUBLISHED\", \"dateUpdated\": \"2026-08-07T21:02:12.997Z\", \"dateReserved\": \"2026-07-23T23:25:28.896Z\", \"assignerOrgId\": \"a0819718-46f1-4df5-94e2-005712e83aaa\", \"datePublished\": \"2026-08-07T16:49:43.853Z\", \"assignerShortName\": \"GitHub_M\"}",
      "dataType": "CVE_RECORD",
      "dataVersion": "5.2"
    }
  }
}

GHSA-29G2-3RMR-QM68

Vulnerability from github – Published: 2026-08-07 16:50 – Updated: 2026-08-07 16:50

Summary

SvelteKit: ReDoS (O(n^2)) in content negotiation — unauthenticated DoS via the Accept header

Details

Impact

SvelteKit is vulnerable to remote CPU-exhaustion DoS attacks via specifically-crafted Accept headers. The impact is mitigated by default header length limits on most platforms, but in the case of raised or absent limits a denial of service is possible.

Patches

The vulnerability is patched in @sveltejs/kit version 2.70.2.

Severity

5.3 (Medium)


                  
                    CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

Show details on source website

JSON

To clipboard

{
  "affected": [
    {
      "database_specific": {
        "last_known_affected_version_range": "\u003c= 2.70.1"
      },
      "package": {
        "ecosystem": "npm",
        "name": "@sveltejs/kit"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "2.70.2"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-66062"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-1333"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-08-07T16:50:02Z",
    "nvd_published_at": null,
    "severity": "MODERATE"
  },
  "details": "### Impact\nSvelteKit is vulnerable to remote CPU-exhaustion DoS attacks via specifically-crafted `Accept` headers. The impact is mitigated by default header length limits on most platforms, but in the case of raised or absent limits a denial of service is possible.\n\n### Patches\nThe vulnerability is patched in `@sveltejs/kit` version 2.70.2.",
  "id": "GHSA-29g2-3rmr-qm68",
  "modified": "2026-08-07T16:50:02Z",
  "published": "2026-08-07T16:50:02Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/sveltejs/kit/security/advisories/GHSA-29g2-3rmr-qm68"
    },
    {
      "type": "WEB",
      "url": "https://github.com/sveltejs/kit/commit/82712fc02c24b1dcf5b25d7a52129cd8455f04f5"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/sveltejs/kit"
    },
    {
      "type": "WEB",
      "url": "https://github.com/sveltejs/kit/releases/tag/@sveltejs/kit@2.70.2"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L",
      "type": "CVSS_V3"
    }
  ],
  "summary": "SvelteKit: ReDoS (O(n^2)) in content negotiation \u2014 unauthenticated DoS via the Accept header"
}

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