CVE-2026-40476: Webonyx Graphql-PHP

High severity, CVSS 7.5. EPSS: 0.7% chance of exploitation in the next 30 days.

graphql-go is a Go implementation of GraphQL. In versions 15.31.4 and below, the OverlappingFieldsCanBeMerged validation rule performs O(n²) pairwise comparisons of fields sharing the same response name. An attacker can send a query with thousands of repeated identical fields, causing excessive CPU usage during validation before execution begins. This is not mitigated by existing QueryDepth or QueryComplexity rules. This issue has been fixed in version 15.31.5.

Affected products

• Webonyx Graphql-PHP: before 15.31.5 (fixed in 15.31.5)

Published 2026-04-17. Last modified 2026-09-14.