Vulnerability-Lookup

CVE-2026-41248 (GCVE-0-2026-41248)

Vulnerability from cvelistv5 – Published: 2026-04-24 21:04 – Updated: 2026-04-27 13:46

Title

Official Clerk JavaScript SDKs: Middleware-based route protection bypass

Summary

Clerk JavaScript is the official JavaScript repository for Clerk authentication. createRouteMatcher in @clerk/nextjs, @clerk/nuxt, and @clerk/astro can be bypassed by certain crafted requests, allowing them to skip middleware gating and reach downstream handlers. This vulnerability is fixed in @clerk/astro 1.5.7, 2.17.10, and 3.0.15; @clerk/nextjs 5.7.6, 6.39.2, and 7.2.1; @clerk/nuxt 1.13.28 and 2.2.2; and @clerk/shared 2.22.1, 3.47.4, anc 4.8.1

Severity

9.1 (Critical)


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

SSVC

Exploitation: none Automatable: no Technical Impact: total

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2026-04-27 13:46 UTC

CWE

CWE-436 - Interpretation Conflict
CWE-863 - Incorrect Authorization

Assigner

GitHub_M mitre root

References

1 reference

URL	Tags
https://github.com/clerk/javascript/security/advi…	x_refsource_CONFIRM

Impacted products

4 products

Vendor	Product	Version	CPE status
clerk	astro	Affected: >= 0.0.1, < 1.5.7 Affected: >= 2.0.0-snapshot.v20241206174604, <= 2.17.9 Affected: >= 3.0.0, < 3.0.15	guessed
clerk	nextjs	Affected: >= 5.0.0, < 5.7.6 Affected: >= 6.0.0-snapshot.vb87a27f, < 6.39.2 Affected: >= 7.0.0, < 7.2.1	guessed
clerk	nuxt	Affected: >= 1.1.0, < 1.13.28 Affected: >= 2.0.0, < 2.2.2	guessed
clerk	shared	Affected: >= 2.20.17, < 2.22.1 Affected: >= 3.0.0-canary.v20250225091530, < 3.47.4 Affected: >= 4.0.0, < 4.8.1	guessed

Show details on NVD website

JSON

To clipboard

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FKIE_CVE-2026-41248

Vulnerability from fkie_nvd - Published: 2026-04-24 21:16 - Updated: 2026-06-17 10:46

Severity

9.1 (Critical) - CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N

Summary

References

	URL	Tags
	security-advisories@github.com	https://github.com/clerk/javascript/security/advisories/GHSA-vqx2-fgx2-5wq9

Impacted products

	Vendor	Product	Version

JSON

To clipboard

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          "product": "astro",
          "vendor": "clerk",
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            },
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              "status": "affected",
              "version": "\u003e= 2.0.0-snapshot.v20241206174604, \u003c= 2.17.9"
            },
            {
              "status": "affected",
              "version": "\u003e= 3.0.0, \u003c 3.0.15"
            }
          ]
        },
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          "vendor": "clerk",
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            },
            {
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            },
            {
              "status": "affected",
              "version": "\u003e= 7.0.0, \u003c 7.2.1"
            }
          ]
        },
        {
          "product": "nuxt",
          "vendor": "clerk",
          "versions": [
            {
              "status": "affected",
              "version": "\u003e= 1.1.0, \u003c 1.13.28"
            },
            {
              "status": "affected",
              "version": "\u003e= 2.0.0, \u003c 2.2.2"
            }
          ]
        },
        {
          "product": "shared",
          "vendor": "clerk",
          "versions": [
            {
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              "version": "\u003e= 2.20.17, \u003c 2.22.1"
            },
            {
              "status": "affected",
              "version": "\u003e= 3.0.0-canary.v20250225091530, \u003c 3.47.4"
            },
            {
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  ],
  "id": "CVE-2026-41248",
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          "userInteraction": "NONE",
          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N",
          "version": "3.1"
        },
        "exploitabilityScore": 3.9,
        "impactScore": 5.2,
        "source": "security-advisories@github.com",
        "type": "Secondary"
      }
    ],
    "ssvcV203": [
      {
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "ssvcData": {
          "id": "CVE-2026-41248",
          "options": [
            {
              "exploitation": "none"
            },
            {
              "automatable": "no"
            },
            {
              "technicalImpact": "total"
            }
          ],
          "role": "CISA Coordinator",
          "timestamp": "2026-04-27T13:46:14.373183Z",
          "version": "2.0.3"
        }
      }
    ]
  },
  "published": "2026-04-24T21:16:18.497",
  "references": [
    {
      "source": "security-advisories@github.com",
      "url": "https://github.com/clerk/javascript/security/advisories/GHSA-vqx2-fgx2-5wq9"
    }
  ],
  "sourceIdentifier": "security-advisories@github.com",
  "vulnStatus": "Deferred",
  "weaknesses": [
    {
      "description": [
        {
          "lang": "en",
          "value": "CWE-436"
        },
        {
          "lang": "en",
          "value": "CWE-863"
        }
      ],
      "source": "security-advisories@github.com",
      "type": "Secondary"
    }
  ]
}

GHSA-VQX2-FGX2-5WQ9

Vulnerability from github – Published: 2026-04-16 21:28 – Updated: 2026-04-27 16:08

Summary

Official Clerk JavaScript SDKs: Middleware-based route protection bypass

Details

Summary

createRouteMatcher in @clerk/nextjs, @clerk/nuxt, and @clerk/astro can be bypassed by certain crafted requests, allowing them to skip middleware gating and reach downstream handlers.

Sessions are not compromised and no existing user can be impersonated - the bypass only affects the middleware-level gating decision.

Who is affected

All apps using createRouteMatcher should upgrade to the patched versions. Patches are drop-in with no API changes. The information below describes the scope of the bypass and helps you understand whether you are potentially affected, but is not a reason to delay the upgrade.

Apps relying only on middleware gating via createRouteMatcher are affected, because a crafted request can skip middleware checks and reach downstream handlers (API routes, server components, etc.). This middleware pattern permits the bypass:

// Next.js example, equivalent patterns exist in Nuxt and Astro
const isProtectedRoute = createRouteMatcher(['/admin(.*)']);

export default clerkMiddleware(async (auth, req) => {
  if (isProtectedRoute(req)) {
    await auth.protect();
  }
});

That said, the bypass is limited to the middleware-level route-matching gate. clerkMiddleware still authenticates the request and auth() reflects the real authentication state of the caller. Auth checks performed inside your route handlers, server components, or server actions continue to work correctly and are not affected. Whether your app is affected in practice depends on whether you have those downstream checks.

External APIs that authenticate each request with a token are also unaffected on those endpoints, since token verification runs independently.

Additionally, this common middleware pattern correctly blocks the bypass at the middleware layer:

// Next.js example, equivalent patterns exist in Nuxt and Astro
const isPublicRoute = createRouteMatcher(['/docs(.*)']);

export default clerkMiddleware(async (auth, req) => {
  if (!isPublicRoute(req)) {
    await auth.protect();
  }
});

@clerk/shared is usually not imported directly in application code, but if you import createPathMatcher from an affected @clerk/shared version, you are also affected. Run npm why @clerk/shared (or your package manager's equivalent) to check your installed version.

Recommended actions

Install the patched version for your framework (pick the one matching your current major):

@clerk/nextjs - v7.x: fixed in 7.2.1 - v6.x: fixed in 6.39.2 - v5.x: fixed in 5.7.6

@clerk/nuxt - v2.x: fixed in 2.2.2 - v1.x: fixed in 1.13.28

@clerk/astro - v3.x: fixed in 3.0.15 - v2.x: fixed in 2.17.10 - v1.x: fixed in 1.5.7

@clerk/shared - v4.x: fixed in 4.8.1 - v3.x: fixed in 3.47.4 - v2.x: fixed in 2.22.1

Workaround

If you cannot upgrade immediately, adding server-side auth checks (auth()) inside your route handlers, server components, or server actions provides defense-in-depth against this bypass.

Timeline

This issue was reported on 13 APR 2026, patched on 15 APR 2026, and publicly disclosed on 15 APR 2026.

Thanks to Christiaan Swiers for the responsible disclosure of this vulnerability.

Severity

9.1 (Critical)


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

Show details on source website

JSON

To clipboard

{
  "affected": [
    {
      "package": {
        "ecosystem": "npm",
        "name": "@clerk/nextjs"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "5.0.0"
            },
            {
              "fixed": "5.7.6"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "package": {
        "ecosystem": "npm",
        "name": "@clerk/nuxt"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "1.1.0"
            },
            {
              "fixed": "1.13.28"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "package": {
        "ecosystem": "npm",
        "name": "@clerk/astro"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0.0.1"
            },
            {
              "fixed": "1.5.7"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "package": {
        "ecosystem": "npm",
        "name": "@clerk/shared"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "2.20.17"
            },
            {
              "fixed": "2.22.1"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "package": {
        "ecosystem": "npm",
        "name": "@clerk/nextjs"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "6.0.0-snapshot.vb87a27f"
            },
            {
              "fixed": "6.39.2"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "package": {
        "ecosystem": "npm",
        "name": "@clerk/nextjs"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "7.0.0"
            },
            {
              "fixed": "7.2.1"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "package": {
        "ecosystem": "npm",
        "name": "@clerk/nuxt"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "2.0.0"
            },
            {
              "fixed": "2.2.2"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "database_specific": {
        "last_known_affected_version_range": "\u003c= 2.17.9"
      },
      "package": {
        "ecosystem": "npm",
        "name": "@clerk/astro"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "2.0.0-snapshot.v20241206174604"
            },
            {
              "fixed": "2.17.10"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "package": {
        "ecosystem": "npm",
        "name": "@clerk/astro"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "3.0.0"
            },
            {
              "fixed": "3.0.15"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "package": {
        "ecosystem": "npm",
        "name": "@clerk/shared"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "3.0.0-canary.v20250225091530"
            },
            {
              "fixed": "3.47.4"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "package": {
        "ecosystem": "npm",
        "name": "@clerk/shared"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "4.0.0"
            },
            {
              "fixed": "4.8.1"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-41248"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-436",
      "CWE-863"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-04-16T21:28:26Z",
    "nvd_published_at": "2026-04-24T21:16:18Z",
    "severity": "CRITICAL"
  },
  "details": "## Summary\n\n`createRouteMatcher` in `@clerk/nextjs`, `@clerk/nuxt`, and `@clerk/astro` can be bypassed by certain crafted requests, allowing them to skip middleware gating and reach downstream handlers.\n\nSessions are not compromised and no existing user can be impersonated - the bypass only affects the middleware-level gating decision.\n\n## Who is affected\n\nAll apps using `createRouteMatcher` should upgrade to the patched versions. Patches are drop-in with no API changes. The information below describes the scope of the bypass and helps you understand whether you are potentially affected, but is not a reason to delay the upgrade.\n\nApps relying only on middleware gating via `createRouteMatcher` are affected, because a crafted request can skip middleware checks and reach downstream handlers (API routes, server components, etc.). This middleware pattern permits the bypass:\n\n```ts\n// Next.js example, equivalent patterns exist in Nuxt and Astro\nconst isProtectedRoute = createRouteMatcher([\u0027/admin(.*)\u0027]);\n\nexport default clerkMiddleware(async (auth, req) =\u003e {\n  if (isProtectedRoute(req)) {\n    await auth.protect();\n  }\n});\n```\n\nThat said, the bypass is limited to the middleware-level route-matching gate. `clerkMiddleware` still authenticates the request and `auth()` reflects the real authentication state of the caller. Auth checks performed inside your route handlers, server components, or server actions continue to work correctly and are not affected. Whether your app is affected in practice depends on whether you have those downstream checks.\n\nExternal APIs that authenticate each request with a token are also unaffected on those endpoints, since token verification runs independently.\n\nAdditionally, this common middleware pattern correctly blocks the bypass at the middleware layer:\n\n```ts\n// Next.js example, equivalent patterns exist in Nuxt and Astro\nconst isPublicRoute = createRouteMatcher([\u0027/docs(.*)\u0027]);\n\nexport default clerkMiddleware(async (auth, req) =\u003e {\n  if (!isPublicRoute(req)) {\n    await auth.protect();\n  }\n});\n```\n\n`@clerk/shared` is usually not imported directly in application code, but if you import `createPathMatcher` from an affected `@clerk/shared` version, you are also affected. Run `npm why @clerk/shared` (or your package manager\u0027s equivalent) to check your installed version.\n\n## Recommended actions\n\nInstall the patched version for your framework (pick the one matching your current major):\n\n**`@clerk/nextjs`**\n- v7.x: fixed in `7.2.1`\n- v6.x: fixed in `6.39.2`\n- v5.x: fixed in `5.7.6`\n\n**`@clerk/nuxt`**\n- v2.x: fixed in `2.2.2`\n- v1.x: fixed in `1.13.28`\n\n**`@clerk/astro`**\n- v3.x: fixed in `3.0.15`\n- v2.x: fixed in `2.17.10`\n- v1.x: fixed in `1.5.7`\n\n**`@clerk/shared`**\n- v4.x: fixed in `4.8.1`\n- v3.x: fixed in `3.47.4`\n- v2.x: fixed in `2.22.1`\n\n## Workaround\n\nIf you cannot upgrade immediately, adding server-side auth checks (`auth()`) inside your route handlers, server components, or server actions provides defense-in-depth against this bypass.\n\n## Timeline\n\nThis issue was reported on 13 APR 2026, patched on 15 APR 2026, and publicly disclosed on 15 APR 2026.\n\nThanks to [Christiaan Swiers](https://github.com/YouGina) for the responsible disclosure of this vulnerability.",
  "id": "GHSA-vqx2-fgx2-5wq9",
  "modified": "2026-04-27T16:08:38Z",
  "published": "2026-04-16T21:28:26Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/clerk/javascript/security/advisories/GHSA-vqx2-fgx2-5wq9"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-41248"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/clerk/javascript"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "Official Clerk JavaScript SDKs: Middleware-based route protection bypass"
}

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.
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.
Browse all ATT&CK techniques and the vulnerabilities related to each.

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Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.

Action not permitted

CVE-2026-41248 (GCVE-0-2026-41248)

FKIE_CVE-2026-41248

GHSA-VQX2-FGX2-5WQ9

Summary

Who is affected

Recommended actions

Workaround

Timeline

Tags

Sightings

Nomenclature

Related by attack behaviour