CVE-2026-63421 is a high-severity (CVSS 7.5) Improper Input Validation vulnerability in @keystone-6/core. O3 Security confirms whether CVE-2026-63421 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
Keystone vulnerable to `graphql.maxTake` bypass with negative `take`
Real-World Exposure
How broadly this vulnerability is actually deployed: weekly install volume shows current usage, and reverse-dependency count shows how many other packages break if it stays unpatched.
@keystone-6/corenpmDescription
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 Security Scanner and validated by their team.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | @keystone-6/core | all versions | 6.5.3 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for @keystone-6/core. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update @keystone-6/core to 6.5.3 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-63421 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether CVE-2026-63421 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to CVE-2026-63421. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2026-63421 in your dependencies?
O3 detects CVE-2026-63421 across npm dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.