Vulnerability-Lookup

CVE-2026-84428 (GCVE-0-2026-84428)

Vulnerability from cvelistv5 – Published: 2026-09-04 10:24 – Updated: 2026-09-04 16:06

Title

fastify vulnerable to header validation bypass via incomplete schema case normalization

Summary

fastify versions before 5.12.2 implement the case-insensitive nature of HTTP header names by lowercasing names in a route's header schema before compiling it, but the transformation is incomplete: it lowercases the properties keys and the root-level required array, and does not lowercase the trigger and dependent names inside the JSON Schema Draft 7 dependencies keyword. Because Node stores request header names in lowercase, a canonical-case dependency such as requiring an authentication header whenever a privileged-mode header is present never matches, and the presence assertion is silently skipped. An unauthenticated remote client can therefore send the header that activates a privileged branch while omitting the header the dependency was meant to require, bypassing the conditional check. Users should upgrade to fastify 5.12.2 or later.

Severity

7.5 (High)


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

SSVC

Exploitation: none Automatable: yes Technical Impact: partial

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2026-09-04 16:04 UTC

CWE

CWE-178 - Improper Handling of Case Sensitivity

Assigner

openjs CNA under the redhat root

CNA scorecard C 66/100 over 142 records in the last 180 days details

References

2 references

URL	Tags
https://github.com/fastify/fastify/security/advis…
https://cna.openjsf.org/security-advisories.html

Impacted products

1 product

Vendor	Product	Version	CPE status
fastify	fastify	Affected: 0 , < 5.12.2 (semver) Unaffected: 5.12.2 (semver)	guessed

Credits

schecthellraiser606 mcollina UlisesGascon

Show details on NVD website

JSON

To clipboard

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FKIE_CVE-2026-84428

Vulnerability from fkie_nvd - Published: 2026-09-04 11:17 - Updated: 2026-09-15 19:54

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
	ce714d77-add3-4f53-aff5-83d477b104bb	https://cna.openjsf.org/security-advisories.html	Third Party Advisory
	ce714d77-add3-4f53-aff5-83d477b104bb	https://github.com/fastify/fastify/security/advisories/GHSA-9q9j-q6p8-xq58	Mitigation, Vendor Advisory

Impacted products

	Vendor	Product	Version
	fastify	fastify	*

JSON

To clipboard

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GHSA-9Q9J-Q6P8-XQ58

Vulnerability from github – Published: 2026-09-30 23:44 – Updated: 2026-09-30 23:44

Summary

fastify vulnerable to header validation bypass via incomplete schema case normalization

Details

Impact

Fastify lowercases header-schema property names before compiling the schema, because Node.js stores request header names in lowercase. That normalization was incomplete: it lowercased only top-level properties keys and the root required array, and did not lowercase the JSON Schema Draft 7 dependencies keyword (its trigger keys and dependent property names) or names in nested subschemas. As a result, a header schema that uses dependencies to require one header when another is present (for example X-Admin requiring X-Admin-Token) never matches the lowercased request headers, so the dependency assertion is silently skipped. An unauthenticated remote client can send the header that activates a privileged path while omitting the header the dependency was meant to require, bypassing a schema-enforced security control. The header schema is idiomatic, valid JSON Schema Draft 7, and no custom validator, malformed request, or misconfiguration is required.

Patches

Header-schema names are now normalized across all schema positions (properties, required, dependencies, dependentRequired, dependentSchemas, and nested subschemas). Patched in fastify 5.12.2. The fix is also included in the 6.0.0 release. Header schemas referenced through an external shared $ref (registered with addSchema) are not reached by this normalization and now emit an FSTSEC002 startup warning; inline the header schema to keep case-insensitive assertions in effect.

Workarounds

If upgrading is not immediately possible, write header-schema names in lowercase so the dependencies and other case-sensitive assertions match Node's lowercased request headers, or enforce the cross-header requirement in an onRequest or preValidation hook instead of the schema.

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

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        "name": "fastify"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "5.12.2"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-84428"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-178"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-09-30T23:44:27Z",
    "nvd_published_at": "2026-09-04T11:17:19Z",
    "severity": "HIGH"
  },
  "details": "### Impact\n\nFastify lowercases header-schema property names before compiling the schema, because Node.js stores request header names in lowercase. That normalization was incomplete: it lowercased only top-level `properties` keys and the root `required` array, and did not lowercase the JSON Schema Draft 7 `dependencies` keyword (its trigger keys and dependent property names) or names in nested subschemas. As a result, a header schema that uses `dependencies` to require one header when another is present (for example `X-Admin` requiring `X-Admin-Token`) never matches the lowercased request headers, so the dependency assertion is silently skipped. An unauthenticated remote client can send the header that activates a privileged path while omitting the header the dependency was meant to require, bypassing a schema-enforced security control. The header schema is idiomatic, valid JSON Schema Draft 7, and no custom validator, malformed request, or misconfiguration is required.\n\n### Patches\n\nHeader-schema names are now normalized across all schema positions (`properties`, `required`, `dependencies`, `dependentRequired`, `dependentSchemas`, and nested subschemas). Patched in fastify `5.12.2`. The fix is also included in the `6.0.0` release. Header schemas referenced through an external shared `$ref` (registered with `addSchema`) are not reached by this normalization and now emit an `FSTSEC002` startup warning; inline the header schema to keep case-insensitive assertions in effect.\n\n### Workarounds\n\nIf upgrading is not immediately possible, write header-schema names in lowercase so the `dependencies` and other case-sensitive assertions match Node\u0027s lowercased request headers, or enforce the cross-header requirement in an `onRequest` or `preValidation` hook instead of the schema.",
  "id": "GHSA-9q9j-q6p8-xq58",
  "modified": "2026-09-30T23:44:27Z",
  "published": "2026-09-30T23:44:27Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/fastify/fastify/security/advisories/GHSA-9q9j-q6p8-xq58"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-84428"
    },
    {
      "type": "WEB",
      "url": "https://github.com/fastify/fastify/commit/179619c8e99d54924309b9933402151ef9af37e0"
    },
    {
      "type": "WEB",
      "url": "https://cna.openjsf.org/security-advisories.html"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/fastify/fastify"
    },
    {
      "type": "WEB",
      "url": "https://github.com/fastify/fastify/releases/tag/v5.12.2"
    }
  ],
  "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 vulnerable to header validation bypass via incomplete schema case normalization"
}

RHSA-2026:84734

Vulnerability from csaf_redhat - Published: 2026-10-19 08:52 - Updated: 2026-11-14 04:47

Summary

Red Hat Security Advisory: RHOAI 3.4.5 - Red Hat OpenShift AI

Severity

Critical

Scope

298 vulnerabilities in this advisory, including CVE-2026-84428.

CVE-2026-84428

A flaw was found in fastify. Due to incomplete case normalization of HTTP header names within a route's header schema, specifically within the JSON Schema Draft 7 dependencies keyword, an unauthenticated remote attacker can bypass intended conditional checks. This allows the attacker to send headers that activate privileged functionality without providing the required authentication headers, leading to an authorization bypass.

7.5 (High)


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

Fixed: 32 products Known not affected: 289 products

https://access.redhat.com/errata/RHSA-2026:84734

Open the full advisory

RHSA-2026:86891

Vulnerability from csaf_redhat - Published: 2026-10-21 11:37 - Updated: 2026-11-14 02:33

Summary

Red Hat Security Advisory: RHOAI 3.5.2 - Red Hat OpenShift AI

Severity

Critical

Scope

93 vulnerabilities in this advisory, including CVE-2026-84428.

CVE-2026-84428

7.5 (High)


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

Fixed: 44 products Known not affected: 330 products

https://access.redhat.com/errata/RHSA-2026:86891

Open the full advisory

RHSA-2026:87410

Vulnerability from csaf_redhat - Published: 2026-10-21 21:07 - Updated: 2026-11-14 04:47

Summary

Red Hat Security Advisory: RHOAI 2.25.12 - Red Hat OpenShift AI

Severity

Critical

Scope

177 vulnerabilities in this advisory, including CVE-2026-84428.

CVE-2026-84428

7.5 (High)


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

Fixed: 8 products Known not affected: 197 products

https://access.redhat.com/errata/RHSA-2026:87410

Open the full advisory

RHSA-2026:90321

Vulnerability from csaf_redhat - Published: 2026-10-26 14:24 - Updated: 2026-11-13 16:45

Summary

Red Hat Security Advisory: Red Hat OpenShift Dev Spaces 3.31.0 Release.

Severity

Critical

Scope

105 vulnerabilities in this advisory, including CVE-2026-84428.

CVE-2026-84428

7.5 (High)


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

Fixed: 4 products Known not affected: 57 products

https://access.redhat.com/errata/RHSA-2026:90321

Open the full advisory

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.

Vulnerability timeline

Sightings and recorded dates, grouped by day · UTC

Order JSON

How durations are calculated

Following the VTEM framework (Black Hat USA 2015), time to patch starts when the vendor or a coordinator was informed, total time to patch at discovery, and disclosure to patch at public disclosure; vendor response time runs from the report to its acknowledgement. Time to exploit and time unpatched start at the earliest discovery or report, falling back to public disclosure. Unpatched time ends at the first recorded patch, or the calculation time when no patch is recorded. Exploitation to patch shows the interval between those two events; a published proof of concept is a public exploit, not exploitation.

Each result shows its source dates. A negative interval means the end event came first; when date-only inputs leave the order open, the result says so. Date-only inputs are approximate. The earliest evidence wins: KEV report dates and sightings are labelled as such. Records describing another vulnerability are listed but never calculated from, and a PoC alone does not establish exploitation. Missing patch evidence does not prove that no patch exists. Filters below change the event list only.

Publication & reservation Sightings KEV catalogs Other timestamps

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

Related by attack behaviour

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-2026-84428 (GCVE-0-2026-84428)

FKIE_CVE-2026-84428

GHSA-9Q9J-Q6P8-XQ58

Impact

Patches

Workarounds

RHSA-2026:84734

RHSA-2026:86891

RHSA-2026:87410

RHSA-2026:90321

Tags

Sightings

Nomenclature

Vulnerability timeline

Related by attack behaviour