EUVD-2026-17961

Description

### Summary A Path Traversal vulnerability in `@tinacms/graphql` allows unauthenticated users to write and overwrite arbitrary files within the project root. This is achieved by manipulating the `relativePath` parameter in GraphQL mutations. The impact includes the ability to replace critical server configuration files and potentially execute arbitrary commands by sabotaging build scripts. ### Details The vulnerability exists in the path validation logic within `@tinacms/graphql`. Specifically, the regex-based validation in `getValidatedPath` fails to recognize backslashes (`\`) as directory separators on non-Windows platforms (Mac/Linux). An attacker can provide a path like `x\..\..\..\package.json`, which bypasses the validation check but is subsequently treated as a traversal path during file I/O operations by the underlying `fs` modules and path normalization utilities. Incriminated code areas: - [packages/@tinacms/graphql/src/database/bridge/filesystem.ts](tinacms/packages/@tinacms/graphql/src/database/bridge/filesystem.ts): [assertWithinBase](tinacms/graphql/src/database/bridge/filesystem.ts#7-35) function. - [packages/@tinacms/graphql/src/resolver/index.ts](tinacms/packages/@tinacms/graphql/src/resolver/index.ts): `getValidatedPath` function. ### PoC 1. Start the TinaCMS development server. 2. Send a malicious GraphQL mutation to overwrite a project file (e.g., [package.json](tinacms/examples/tina-self-hosted-demo/package.json)): ```bash curl -X POST http://localhost:4001/graphql \ -H "Content-Type: application/json" \ -d '{"query": "mutation { updateDocument(collection: \"global\", relativePath: \"x\\\\..\\\\..\\\\..\\\\package.json\", params: { global: { header: { name: \"OVERWRITTEN\" } } }) { __typename } }"}' ``` 3. Observe that the root [package.json](tinacms/examples/tina-self-hosted-demo/package.json) has been replaced with the provided payload. <img width="1424" height="516" alt="2026-03-15_12-24-05 PM" src="https://github.com/user-attachments/assets/9fdf94ce-2183-4a24-9cd9-48f21deb9768" /> <img width="1387" height="774" alt="2026-03-15_12-27-33 PM" src="https://github.com/user-attachments/assets/676f083b-f934-4cf2-978b-bb2fabee0216" /> ### Impact This is an **Arbitrary File Write** vulnerability. Any unauthenticated user with network access to the GraphQL API can: - Overwrite critical server configuration files (e.g., [package.json](tinacms/examples/tina-self-hosted-demo/package.json), [tsconfig.json](tinacms/examples/tina-self-hosted-demo/tsconfig.json)). - Host malicious scripts in the `public/` directory for client-side attacks. - Perform **Arbitrary Code Execution** by modifying build scripts or server-side logic files that are subsequently executed by the environment. **Weaknesses:** - **CWE-22**: Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal') - **CWE-73**: External Control of File Name or Path

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