CVE-2026-104852 GraphQL Tools has prototype pollution in well-established utility function `mergeDeep`
An attacker can exploit prototype pollution in GraphQL Tools to overwrite Function.prototype.call, leading to code execution or denial of service.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-104852?
CVE-2026-104852 is a high-severity code injection vulnerability in ardatan graphql-tools, published on 5 Oct 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
GraphQL Tools provides utilities for building, stitching, and mocking GraphQL schemas. Prior to 12.0.1, the GraphQL Tools utils package's mergeDeep function follows inherited properties while recursively merging source objects and does not exclude __proto__, constructor, or prototype keys. An unauthenticated GraphQL client can alias fields to those names so responses from two subgraphs collide during ordinary supergraph result merging, causing mergeDeep to traverse Object and Function prototypes and overwrite Function.prototype.call with a subgraph-supplied value. This breaks subsequent requests in the process until restart. This issue is fixed in version 12.0.1.
Weakness: CWE-1321
Which versions are affected by CVE-2026-104852?
2 open source packages ship an affected version, including @graphql-tools/utils.
| Package | Affected | Fixed in |
|---|---|---|
@graphql-tools/utils npm | All versions | 12.0.1 |
@graphql-tools/utils npm | All versions | 12.0.1 |
How do I fix CVE-2026-104852?
Upgrade @graphql-tools/utils to 12.0.1 or later.
Upgrade, and never evaluate templates, expressions or code built from user input. More about Code injection.
Is CVE-2026-104852 being exploited?
There is no known exploitation of CVE-2026-104852 in the wild and no public exploit code.
Sources
Also known as CLSA-2026-1791291395, CLSA-2026-1792937883, CLSA-2026-1793018204, CLSA-2026-1793019970, CLSA-2026-1793020728, CLSA-2026-1793021479 and 10 more.