CVE-2026-63421Network attack vector

Unauthenticated service exhaustion via negative take values

Published Aug 21, 2026 · Updated Aug 21, 2026

Improper input validation in Keystone before 6.5.3 allows remote attackers to exhaust service resources through GraphQL queries. The findMany resolver compares the signed take argument directly with graphql.maxTake instead of comparing its absolute value, so a sufficiently negative value passes the bound. Unauthenticated access to an exposed GraphQL endpoint is sufficient, and oversized findMany or relationship responses can interrupt the service by exhausting resources.

CVSS severity7.5
High
EPSS probability0.47%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper input validation in Keystone before 6.5.3 allows remote attackers to exhaust service resources through GraphQL queries. The findMany resolver compares the signed take argument directly with graphql.maxTake instead of comparing its absolute value, so a sufficiently negative value passes the bound. Unauthenticated access to an exposed GraphQL endpoint is sufficient, and oversized findMany or relationship responses can interrupt the service by exhausting resources.

The record

CVE
CVE-2026-63421
Published
Aug 21, 2026
Updated
Aug 21, 2026
Vendor
KeystoneJS
Product
Keystone
Classifications
CWE-20, CWE-480, T1499.002
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Aug 21, 2026CVE publishedPublication date reported by the CVE source.
  2. Aug 21, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=< 6.5.3

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

KeystoneJS · Keystoneversion=< 6.5.3

Published CVSS scores

7.5GitHubCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-20Improper Input Validation
CWE-480Use of Incorrect Operator
T1499.002Service Exhaustion

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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