# CVE-2026-63421: Keystone: `graphql.maxTake` bypass with negative `take`

> Attackers can bypass GraphQL take limits using negative values to retrieve excessive records, potentially causing resource exhaustion.

- **Severity:** High 7.5 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 21 Aug 2026
- **Updated:** 26 Aug 2026
- **Also known as:** GHSA-cqmq-8755-7xvh

## What is CVE-2026-63421?

CVE-2026-63421 is a high-severity vulnerability in keystonejs keystone, published on 21 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

Keystone is a content management system for Node.js. Prior to 6.5.3, the findMany resolver in packages/core/src/lib/core/queries/resolvers.ts compares the signed take argument directly with graphql.maxTake, allowing a remote unauthenticated GraphQL client to provide a negative take value whose magnitude exceeds the configured bound. The bypass also applies to relationship queries and can return more records than the developer intended, potentially exhausting service resources. This issue is fixed in version 6.5.3.

Weakness: CWE-480 (Use of Incorrect Operator), CWE-20 (Improper Input Validation)

## Which versions are affected by CVE-2026-63421?

2 open source packages ship an affected version, including @keystone-6/core.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `@keystone-6/core` | npm | All versions | 6.5.3 |
| `@keystone-6/core` | npm | All versions | 6.5.3 |

## How do I fix CVE-2026-63421?

Upgrade @keystone-6/core to 6.5.3 or later.

## Is CVE-2026-63421 being exploited?

There is no known exploitation of CVE-2026-63421 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-63421 and fix it if it is affected.

What it is: CVE-2026-63421 is a high-severity vulnerability in keystonejs keystone, published on 21 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-63421 in the wild and no public exploit code.

Affected packages and fixed versions:
- @keystone-6/core (npm): affected all versions; fixed in 6.5.3
- @keystone-6/core (npm): affected all versions; fixed in 6.5.3

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-63421/ (Markdown: https://insights.sbomify.com/CVE-2026-63421/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-63421
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-63421
- OSV: https://osv.dev/vulnerability/CVE-2026-63421

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-63421/
Summaries are generated and may contain mistakes; the official description above is the record.