Vulnerability-Lookup

CVE-2026-25223 (GCVE-0-2026-25223)

Vulnerability from cvelistv5 – Published: 2026-02-03 21:21 – Updated: 2026-02-03 21:21

Title

Fastify's Content-Type header tab character allows body validation bypass

Summary

Fastify is a fast and low overhead web framework, for Node.js. Prior to version 5.7.2, a validation bypass vulnerability exists in Fastify where request body validation schemas specified by Content-Type can be completely circumvented. By appending a tab character (\t) followed by arbitrary content to the Content-Type header, attackers can bypass body validation while the server still processes the body as the original content type. This issue has been patched in version 5.7.2.

Severity ?

7.5 (High)


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

CWE

CWE-436 - Interpretation Conflict

Assigner

GitHub_M

References

URL

Tags

	https://github.com/fastify/fastify/security/advis…	x_refsource_CONFIRM
	https://github.com/fastify/fastify/commit/32d7b6a…	x_refsource_MISC
	https://hackerone.com/reports/3464114	x_refsource_MISC
	https://fastify.dev/docs/latest/Reference/Validat…	x_refsource_MISC
	https://github.com/fastify/fastify/blob/759e9787b…	x_refsource_MISC
	https://github.com/fastify/fastify/blob/759e9787b…	x_refsource_MISC

Impacted products

	Vendor	Product	Version
	fastify	fastify	Affected: < 5.7.2

Show details on NVD website

JSON

To clipboard

{
  "containers": {
    "cna": {
      "affected": [
        {
          "product": "fastify",
          "vendor": "fastify",
          "versions": [
            {
              "status": "affected",
              "version": "\u003c 5.7.2"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "Fastify is a fast and low overhead web framework, for Node.js. Prior to version 5.7.2, a validation bypass vulnerability exists in Fastify where request body validation schemas specified by Content-Type can be completely circumvented. By appending a tab character (\\t) followed by arbitrary content to the Content-Type header, attackers can bypass body validation while the server still processes the body as the original content type. This issue has been patched in version 5.7.2."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "attackComplexity": "LOW",
            "attackVector": "NETWORK",
            "availabilityImpact": "NONE",
            "baseScore": 7.5,
            "baseSeverity": "HIGH",
            "confidentialityImpact": "NONE",
            "integrityImpact": "HIGH",
            "privilegesRequired": "NONE",
            "scope": "UNCHANGED",
            "userInteraction": "NONE",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N",
            "version": "3.1"
          }
        }
      ],
      "problemTypes": [
        {
          "descriptions": [
            {
              "cweId": "CWE-436",
              "description": "CWE-436: Interpretation Conflict",
              "lang": "en",
              "type": "CWE"
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-02-03T21:21:40.268Z",
        "orgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
        "shortName": "GitHub_M"
      },
      "references": [
        {
          "name": "https://github.com/fastify/fastify/security/advisories/GHSA-jx2c-rxcm-jvmq",
          "tags": [
            "x_refsource_CONFIRM"
          ],
          "url": "https://github.com/fastify/fastify/security/advisories/GHSA-jx2c-rxcm-jvmq"
        },
        {
          "name": "https://github.com/fastify/fastify/commit/32d7b6add39ddf082d92579a58bea7018c5ac821",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/fastify/fastify/commit/32d7b6add39ddf082d92579a58bea7018c5ac821"
        },
        {
          "name": "https://hackerone.com/reports/3464114",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://hackerone.com/reports/3464114"
        },
        {
          "name": "https://fastify.dev/docs/latest/Reference/Validation-and-Serialization",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://fastify.dev/docs/latest/Reference/Validation-and-Serialization"
        },
        {
          "name": "https://github.com/fastify/fastify/blob/759e9787b5669abf953068e42a17bffba7521348/lib/content-type-parser.js#L125",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/fastify/fastify/blob/759e9787b5669abf953068e42a17bffba7521348/lib/content-type-parser.js#L125"
        },
        {
          "name": "https://github.com/fastify/fastify/blob/759e9787b5669abf953068e42a17bffba7521348/lib/validation.js#L272",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/fastify/fastify/blob/759e9787b5669abf953068e42a17bffba7521348/lib/validation.js#L272"
        }
      ],
      "source": {
        "advisory": "GHSA-jx2c-rxcm-jvmq",
        "discovery": "UNKNOWN"
      },
      "title": "Fastify\u0027s Content-Type header tab character allows body validation bypass"
    }
  },
  "cveMetadata": {
    "assignerOrgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
    "assignerShortName": "GitHub_M",
    "cveId": "CVE-2026-25223",
    "datePublished": "2026-02-03T21:21:40.268Z",
    "dateReserved": "2026-01-30T14:44:47.327Z",
    "dateUpdated": "2026-02-03T21:21:40.268Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2",
  "vulnerability-lookup:meta": {
    "nvd": "{\"cve\":{\"id\":\"CVE-2026-25223\",\"sourceIdentifier\":\"security-advisories@github.com\",\"published\":\"2026-02-03T22:16:31.130\",\"lastModified\":\"2026-02-03T22:16:31.130\",\"vulnStatus\":\"Received\",\"cveTags\":[],\"descriptions\":[{\"lang\":\"en\",\"value\":\"Fastify is a fast and low overhead web framework, for Node.js. Prior to version 5.7.2, a validation bypass vulnerability exists in Fastify where request body validation schemas specified by Content-Type can be completely circumvented. By appending a tab character (\\\\t) followed by arbitrary content to the Content-Type header, attackers can bypass body validation while the server still processes the body as the original content type. This issue has been patched in version 5.7.2.\"}],\"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:H/A:N\",\"baseScore\":7.5,\"baseSeverity\":\"HIGH\",\"attackVector\":\"NETWORK\",\"attackComplexity\":\"LOW\",\"privilegesRequired\":\"NONE\",\"userInteraction\":\"NONE\",\"scope\":\"UNCHANGED\",\"confidentialityImpact\":\"NONE\",\"integrityImpact\":\"HIGH\",\"availabilityImpact\":\"NONE\"},\"exploitabilityScore\":3.9,\"impactScore\":3.6}]},\"weaknesses\":[{\"source\":\"security-advisories@github.com\",\"type\":\"Primary\",\"description\":[{\"lang\":\"en\",\"value\":\"CWE-436\"}]}],\"references\":[{\"url\":\"https://fastify.dev/docs/latest/Reference/Validation-and-Serialization\",\"source\":\"security-advisories@github.com\"},{\"url\":\"https://github.com/fastify/fastify/blob/759e9787b5669abf953068e42a17bffba7521348/lib/content-type-parser.js#L125\",\"source\":\"security-advisories@github.com\"},{\"url\":\"https://github.com/fastify/fastify/blob/759e9787b5669abf953068e42a17bffba7521348/lib/validation.js#L272\",\"source\":\"security-advisories@github.com\"},{\"url\":\"https://github.com/fastify/fastify/commit/32d7b6add39ddf082d92579a58bea7018c5ac821\",\"source\":\"security-advisories@github.com\"},{\"url\":\"https://github.com/fastify/fastify/security/advisories/GHSA-jx2c-rxcm-jvmq\",\"source\":\"security-advisories@github.com\"},{\"url\":\"https://hackerone.com/reports/3464114\",\"source\":\"security-advisories@github.com\"}]}}"
  }
}

GHSA-JX2C-RXCM-JVMQ

Vulnerability from github – Published: 2026-02-02 22:23 – Updated: 2026-02-02 22:23

Summary

Fastify's Content-Type header tab character allows body validation bypass

Details

Impact

A validation bypass vulnerability exists in Fastify where request body validation schemas specified by Content-Type can be completely circumvented. By appending a tab character (\t) followed by arbitrary content to the Content-Type header, attackers can bypass body validation while the server still processes the body as the original content type.

For example, a request with Content-Type: application/json\ta will bypass JSON schema validation but still be parsed as JSON.

This vulnerability affects all Fastify users who rely on Content-Type-based body validation schemas to enforce data integrity or security constraints. The concrete impact depends on the handler implementation and the level of trust placed in the validated request body, but at the library level, this allows complete bypass of body validation for any handler using Content-Type-discriminated schemas.

This issue is a regression or missed edge case from the fix for a previously reported vulnerability.

Patches

This vulnerability has been patched in Fastify v5.7.2. All users should upgrade to this version or later immediately.

Workarounds

If upgrading is not immediately possible, user can implement a custom onRequest hook to reject requests containing tab characters in the Content-Type header:

fastify.addHook('onRequest', async (request, reply) => {
  const contentType = request.headers['content-type']
  if (contentType && contentType.includes('\t')) {
    reply.code(400).send({ error: 'Invalid Content-Type header' })
  }
})

Resources

https://github.com/fastify/fastify/blob/759e9787b5669abf953068e42a17bffba7521348/lib/validation.js#L272
https://github.com/fastify/fastify/blob/759e9787b5669abf953068e42a17bffba7521348/lib/content-type-parser.js#L125
Fastify Validation and Serialization Documentation
https://hackerone.com/reports/3464114

Severity ?

7.5 (High)


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

Show details on source website

JSON

To clipboard

{
  "affected": [
    {
      "package": {
        "ecosystem": "npm",
        "name": "fastify"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "5.7.2"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-25223"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-436"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-02-02T22:23:29Z",
    "nvd_published_at": null,
    "severity": "HIGH"
  },
  "details": "### Impact\n\nA validation bypass vulnerability exists in Fastify where request body validation schemas specified by Content-Type can be completely circumvented. By appending a tab character (`\\t`) followed by arbitrary content to the Content-Type header, attackers can bypass body validation while the server still processes the body as the original content type.\n\nFor example, a request with `Content-Type: application/json\\ta` will bypass JSON schema validation but still be parsed as JSON.\n\nThis vulnerability affects all Fastify users who rely on Content-Type-based body validation schemas to enforce data integrity or security constraints. The concrete impact depends on the handler implementation and the level of trust placed in the validated request body, but at the library level, this allows complete bypass of body validation for any handler using Content-Type-discriminated schemas.\n\nThis issue is a regression or missed edge case from the fix for a previously reported vulnerability.\n\n### Patches\n\nThis vulnerability has been patched in **Fastify v5.7.2**. All users should upgrade to this version or later immediately.\n\n### Workarounds\n\nIf upgrading is not immediately possible, user can implement a custom `onRequest` hook to reject requests containing tab characters in the Content-Type header:\n\n```javascript\nfastify.addHook(\u0027onRequest\u0027, async (request, reply) =\u003e {\n  const contentType = request.headers[\u0027content-type\u0027]\n  if (contentType \u0026\u0026 contentType.includes(\u0027\\t\u0027)) {\n    reply.code(400).send({ error: \u0027Invalid Content-Type header\u0027 })\n  }\n})\n```\n\n### Resources\n\n- https://github.com/fastify/fastify/blob/759e9787b5669abf953068e42a17bffba7521348/lib/validation.js#L272\n- https://github.com/fastify/fastify/blob/759e9787b5669abf953068e42a17bffba7521348/lib/content-type-parser.js#L125\n- [Fastify Validation and Serialization Documentation](https://fastify.dev/docs/latest/Reference/Validation-and-Serialization/)\n- https://hackerone.com/reports/3464114",
  "id": "GHSA-jx2c-rxcm-jvmq",
  "modified": "2026-02-02T22:23:29Z",
  "published": "2026-02-02T22:23:29Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/fastify/fastify/security/advisories/GHSA-jx2c-rxcm-jvmq"
    },
    {
      "type": "WEB",
      "url": "https://github.com/fastify/fastify/commit/32d7b6add39ddf082d92579a58bea7018c5ac821"
    },
    {
      "type": "WEB",
      "url": "https://hackerone.com/reports/3464114"
    },
    {
      "type": "WEB",
      "url": "https://fastify.dev/docs/latest/Reference/Validation-and-Serialization"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/fastify/fastify"
    },
    {
      "type": "WEB",
      "url": "https://github.com/fastify/fastify/blob/759e9787b5669abf953068e42a17bffba7521348/lib/content-type-parser.js#L125"
    },
    {
      "type": "WEB",
      "url": "https://github.com/fastify/fastify/blob/759e9787b5669abf953068e42a17bffba7521348/lib/validation.js#L272"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "Fastify\u0027s Content-Type header tab character allows body validation bypass"
}

FKIE_CVE-2026-25223

Vulnerability from fkie_nvd - Published: 2026-02-03 22:16 - Updated: 2026-02-03 22:16

Severity ?

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

Summary

References

	URL	Tags
	security-advisories@github.com	https://fastify.dev/docs/latest/Reference/Validation-and-Serialization
	security-advisories@github.com	https://github.com/fastify/fastify/blob/759e9787b5669abf953068e42a17bffba7521348/lib/content-type-parser.js#L125
	security-advisories@github.com	https://github.com/fastify/fastify/blob/759e9787b5669abf953068e42a17bffba7521348/lib/validation.js#L272
	security-advisories@github.com	https://github.com/fastify/fastify/commit/32d7b6add39ddf082d92579a58bea7018c5ac821
	security-advisories@github.com	https://github.com/fastify/fastify/security/advisories/GHSA-jx2c-rxcm-jvmq
	security-advisories@github.com	https://hackerone.com/reports/3464114

Impacted products

	Vendor	Product	Version

JSON

To clipboard

{
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "Fastify is a fast and low overhead web framework, for Node.js. Prior to version 5.7.2, a validation bypass vulnerability exists in Fastify where request body validation schemas specified by Content-Type can be completely circumvented. By appending a tab character (\\t) followed by arbitrary content to the Content-Type header, attackers can bypass body validation while the server still processes the body as the original content type. This issue has been patched in version 5.7.2."
    }
  ],
  "id": "CVE-2026-25223",
  "lastModified": "2026-02-03T22:16:31.130",
  "metrics": {
    "cvssMetricV31": [
      {
        "cvssData": {
          "attackComplexity": "LOW",
          "attackVector": "NETWORK",
          "availabilityImpact": "NONE",
          "baseScore": 7.5,
          "baseSeverity": "HIGH",
          "confidentialityImpact": "NONE",
          "integrityImpact": "HIGH",
          "privilegesRequired": "NONE",
          "scope": "UNCHANGED",
          "userInteraction": "NONE",
          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N",
          "version": "3.1"
        },
        "exploitabilityScore": 3.9,
        "impactScore": 3.6,
        "source": "security-advisories@github.com",
        "type": "Secondary"
      }
    ]
  },
  "published": "2026-02-03T22:16:31.130",
  "references": [
    {
      "source": "security-advisories@github.com",
      "url": "https://fastify.dev/docs/latest/Reference/Validation-and-Serialization"
    },
    {
      "source": "security-advisories@github.com",
      "url": "https://github.com/fastify/fastify/blob/759e9787b5669abf953068e42a17bffba7521348/lib/content-type-parser.js#L125"
    },
    {
      "source": "security-advisories@github.com",
      "url": "https://github.com/fastify/fastify/blob/759e9787b5669abf953068e42a17bffba7521348/lib/validation.js#L272"
    },
    {
      "source": "security-advisories@github.com",
      "url": "https://github.com/fastify/fastify/commit/32d7b6add39ddf082d92579a58bea7018c5ac821"
    },
    {
      "source": "security-advisories@github.com",
      "url": "https://github.com/fastify/fastify/security/advisories/GHSA-jx2c-rxcm-jvmq"
    },
    {
      "source": "security-advisories@github.com",
      "url": "https://hackerone.com/reports/3464114"
    }
  ],
  "sourceIdentifier": "security-advisories@github.com",
  "vulnStatus": "Received",
  "weaknesses": [
    {
      "description": [
        {
          "lang": "en",
          "value": "CWE-436"
        }
      ],
      "source": "security-advisories@github.com",
      "type": "Primary"
    }
  ]
}

Sightings

Author	Source	Type	Date

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.

Action not permitted

CVE-2026-25223 (GCVE-0-2026-25223)

GHSA-JX2C-RXCM-JVMQ

Impact

Patches

Workarounds

Resources

FKIE_CVE-2026-25223

Tags

Sightings

Nomenclature