Bug 2559120 (CVE-2026-75507)

Summary: CVE-2026-75507 graphql-core: graphql-core: Denial of Service via nested inline fragments during query validation
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security <prodsec-ir-bot>
Status: NEW --- QA Contact:
Severity: high Docs Contact:
Priority: high    
Version: unspecifiedCC: aprice, ilpinto, jsamir, ltomasbo, oezr, yguenane, ykashtan
Target Milestone: ---Keywords: Security
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Hardware: All   
OS: Linux   
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A flaw was found in GraphQL-core. An unauthenticated remote attacker could cause a Denial of Service (DoS) by submitting a specially crafted query with nested inline fragments. During query validation, repeated field comparisons consume excessive CPU resources before complexity limits can be enforced, potentially exhausting worker processes and disrupting service availability.
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Description OSIDB Bzimport 2026-10-22 16:23:04 UTC 
GraphQL-core is a Python port of the GraphQL.js reference implementation. From 3.0.0 until 3.2.12 and 3.3.0rc1, the OverlappingFieldsCanBeMerged rule in specified_rules repeatedly compares fields that share response names and recursively re-compares flattened inline fragments during the validation phase. The prior named-fragment memoization does not cover this path, so nested repeated inline fragments can drive quadratic and worst-case O(n²·m²) CPU work before any resolver or AST-based depth or complexity control runs. An unauthenticated remote attacker can submit a shallow, highly compressible GraphQL query that pins a worker process and can saturate a multi-worker service. This issue is fixed in versions 3.2.12 and 3.3.0rc1.