Summary
GraphQL Tools has prototype pollution in well-established utility function mergeDeep
Closed by https://github.com/ardatan/graphql-tools/pull/8423
Mitigated in Hive Gateway by https://github.com/graphql-hive/gateway/pull/2600
A 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.
{
shared {
fieldA
constructor: fieldB {
__proto__: child {
call: value
}
}
}
}
Impact
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
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Frequently Asked Questions
- What is CVE-2026-104852? CVE-2026-104852 is a high-severity security vulnerability in @graphql-tools/utils (npm), affecting versions <= 12.0.0. It is fixed in 12.0.1.
- Which versions of @graphql-tools/utils are affected by CVE-2026-104852? @graphql-tools/utils (npm) versions <= 12.0.0 is affected.
- Is there a fix for CVE-2026-104852? Yes. CVE-2026-104852 is fixed in 12.0.1. Upgrade to this version or later.
- Is CVE-2026-104852 exploitable, and should I be worried? Whether CVE-2026-104852 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether CVE-2026-104852 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix CVE-2026-104852? Upgrade
@graphql-tools/utilsto 12.0.1 or later.