{"id":"GHSA-7mx3-vvmw-hjmv","summary":"GraphQL Tools has prototype pollution in well-established utility function `mergeDeep`","details":"Closed by https://github.com/ardatan/graphql-tools/pull/8423\nMitigated in Hive Gateway by https://github.com/graphql-hive/gateway/pull/2600\n\nA client can alias fields to `constructor`, `__proto__` or `prototype` so that the response keys from two subgraphs collide on those names during result merging. Because `mergeDeep` recursed through inherited properties, the merge walked `{}.constructor` to `Object`, then `Object.__proto__` to `Function.prototype`, and wrote a subgraph-supplied value over `Function.prototype.call`, breaking every subsequent request in the process until restart. This is remotely triggerable by an unauthenticated client with a single query against any supergraph that merges an object from two subgraphs, which is the ordinary `@shareable` or entity case, so it is a denial of service rather than a theoretical hardening issue.\n\n\n```graphql\n{\n  shared {\n    fieldA\n    constructor: fieldB {\n      __proto__: child {\n        call: value\n      }\n    }\n  }\n}\n```","aliases":["CVE-2026-104852"],"modified":"2026-10-05T23:15:09.209533488Z","published":"2026-10-05T22:56:46Z","database_specific":{"github_reviewed":true,"github_reviewed_at":"2026-10-05T22:56:46Z","nvd_published_at":null,"cwe_ids":["CWE-1321"],"severity":"HIGH"},"references":[{"type":"WEB","url":"https://github.com/ardatan/graphql-tools/security/advisories/GHSA-7mx3-vvmw-hjmv"},{"type":"WEB","url":"https://github.com/ardatan/graphql-tools/pull/8423"},{"type":"WEB","url":"https://github.com/graphql-hive/gateway/pull/2600"},{"type":"WEB","url":"https://github.com/ardatan/graphql-tools/commit/0b9529f1988fd36186a7c106a6efe0356f1b7f2e"},{"type":"PACKAGE","url":"https://github.com/ardatan/graphql-tools"},{"type":"WEB","url":"https://github.com/ardatan/graphql-tools/releases/tag/@graphql-tools/utils@12.0.1"}],"affected":[{"package":{"name":"@graphql-tools/utils","ecosystem":"npm","purl":"pkg:npm/%40graphql-tools/utils"},"ranges":[{"type":"SEMVER","events":[{"introduced":"0"},{"fixed":"12.0.1"}]}],"database_specific":{"last_known_affected_version_range":"\u003c= 12.0.0","source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/10/GHSA-7mx3-vvmw-hjmv/GHSA-7mx3-vvmw-hjmv.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V4","score":"CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N"}]}