CVE-2026-63421: @keystone 6/core Keystone Vulnerable To `graphql.maxTake` Bypass Vulnerability

HIGH
Advisory Identifier: GHSA-cqmq-8755-7xvh
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CVSS 7.5
CWE-20 CWE-480
Published
Advisory Summary

CVE-2026-63421 is a HIGH (CVSS 7.5) keystone vulnerable to `graphql.maxtake` bypass vulnerability (CWE-20: Improper Input Validation) affecting @keystone 6/core libraries in the npm ecosystem. The issue involves keystone vulnerable to `graphql.maxtake` bypass with negative `take`. Remediation is available by upgrading affected packages to version 6.5.3.

CVE-2026-63421 at a Glance

CVE Identifier CVE-2026-63421
GHSA Identifier GHSA-cqmq-8755-7xvh
Severity HIGH
CVSS v3.1 Base Score 7.5
CWE Classification CWE-20: Improper Input Validation
Affected Product @keystone 6/core
Package Ecosystem npm
Published Date
Last Updated

Security Impact

CVSS: 7.5

The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H).

Attack Vector Network (AV:N)
Attack Complexity Low (AC:L)
Privileges Required None (PR:N)
User Interaction None (UI:N)
Scope Unchanged (S:U)
Confidentiality None (C:N)
Integrity None (I:N)
Availability High (A:H)

How to Fix CVE-2026-63421

To remediate this vulnerability, upgrade all affected @keystone 6/core dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

@keystone-6/core fixed: 6.5.3 
npm install @keystone-6/core@6.5.3
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

npm ls @keystone-6/core

How to Check if You Are Affected

To determine whether your Node.js application is affected by CVE-2026-63421, inspect your project dependencies using npm:

npm ls @keystone-6/core

Analyze the terminal output to locate any version of @keystone 6/core in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 6.5.3), your application is affected.

Note: The npm ls @keystone-6/core command inspects dependencies declared in your package.json and lockfile; it does not perform automated runtime dynamic scanning.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-20: Improper Input Validation, where the product receives input or data, but it does not validate or incorrectly validates that the input has the properties that are required to process the data safely and correctly. In @keystone 6/core, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

# Summary The value of `graphql.maxTake` can be bypassed by providing a negative input. This can be used to exceed the developer's intended `graphql.maxTake` value, allowing queries to return results in excess of the `graphql.maxTake` value set. # Impact This affects any project relying on `graphql.maxTake` to bound the number of items returned per query. # Patches This issue has been patched in `@keystone-6/core` version `6.5.3`. If you cannot patch, you can workaround this by restricting `take` input values in your GraphQL queries to the bounded value, or by blocking negative values. # Credit This issue was found by [Haxset's](https://haxset.com) Security Scanner and validated by their team.

CVE-2026-63421 Affected @keystone 6/core Versions

1 component(s)
Fixed Versions:
6.5.3
Product / Package Ecosystem Affected Versions Fixed Version
@keystone-6/core
npm/@keystone-6/core
npm
< 6.5.3
6.5.3

References

GitHub Advisory / Wiki ADVISORY
https://github.com/keystonejs/keystone/security/advisories/GHSA-cqmq-8755-7xvh
@keystone 6/core Source Repository REPOSITORY
https://github.com/keystonejs/keystone/pull/9859
Security Fix Commit FIX COMMIT
https://github.com/keystonejs/keystone/commit/9fb88b246950ce4de754a43fe6416f20403577b1
@keystone 6/core Source Repository REPOSITORY
https://github.com/keystonejs/keystone
@keystone 6/core Release RELEASE
https://github.com/keystonejs/keystone/releases/tag/@keystone-6/core@6.5.3

Frequently Asked Questions

What is CVE-2026-63421?
CVE-2026-63421 is a security vulnerability in @keystone 6/core involving Keystone vulnerable to `graphql.maxTake` bypass with negative `take` under CWE-20: Improper Input Validation.
Which @keystone 6/core versions are affected?
Affected versions include releases prior to 6.5.3 across affected packages: @keystone-6/core.
What version fixes CVE-2026-63421?
Upgrading to 6.5.3 (or the latest patched release for your respective branch) resolves the vulnerability.
Is @keystone-6/core affected?
Yes, @keystone-6/core is affected in releases prior to 6.5.3. Upgrade your dependency to 6.5.3 or later.
What is the CVSS score of CVE-2026-63421?
CVE-2026-63421 has a CVSS v3.1 base score of 7.5 (HIGH) with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.
What CWE is associated with CVE-2026-63421?
CVE-2026-63421 is classified under CWE-20: Improper Input Validation (The product receives input or data, but it does not validate or incorrectly validates that the input has the properties that are required to process the data safely and correctly.).
How can I check npm dependencies for CVE-2026-63421?
Run the dependency tree command: 'npm ls @keystone-6/core'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-cqmq-8755-7xvh",
  "modified" : "2026-08-21T20:55:11Z",
  "published" : "2026-08-21T20:55:11Z",
  "aliases" : [ "CVE-2026-63421" ],
  "summary" : "Keystone vulnerable to `graphql.maxTake` bypass with negative `take`",
  "details" : "# Summary\nThe value of `graphql.maxTake` can be bypassed by providing a negative input.\nThis can be used to exceed the developer's intended `graphql.maxTake` value, allowing queries to return results in excess of the `graphql.maxTake` value set.\n\n# Impact\nThis affects any project relying on `graphql.maxTake` to bound the number of items returned per query.\n\n# Patches\nThis issue has been patched in `@keystone-6/core` version `6.5.3`.\n\nIf you cannot patch, you can workaround this by restricting `take` input values in your GraphQL queries to the bounded value, or by blocking negative values.\n\n# Credit\nThis issue was found by [Haxset's](https://haxset.com) Security Scanner and validated by their team.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "npm",
      "name" : "@keystone-6/core"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "6.5.3"
      } ]
    } ],
    "database_specific" : {
      "last_known_affected_version_range" : "<= 6.5.2"
    }
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/keystonejs/keystone/security/advisories/GHSA-cqmq-8755-7xvh"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/keystonejs/keystone/pull/9859"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/keystonejs/keystone/commit/9fb88b246950ce4de754a43fe6416f20403577b1"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/keystonejs/keystone"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/keystonejs/keystone/releases/tag/@keystone-6/core@6.5.3"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-20", "CWE-480" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-08-21T20:55:11Z",
    "nvd_published_at" : null
  }
}