GHSA-9R75-G2CR-3H76

createWebhook() in Vercel Workflow DevKit accepts a user-specified token parameter that serves as the credential for the public webhook endpoint /.well-known/workflow/v1/webhook/{token}. Official documentation recommended predictable token patterns, making it possible for an unauthenticated remote attacker to guess the token and inject arbitrary payloads into the workflow execution context.

Workarounds

In case a version upgrade is not possible, avoid passing predictable or guessable values to the token parameter of createWebhook(). Instead, users can either

• switch from createWebhook() to createHook() instead and programmatically resume hooks using resumeHook() instead of the public webhook endpoint, or
• use createWebhook() without passing a user-provided token, which uses a non-guessable random nanoid by default.

An attacker who guesses a webhook token can resume the associated workflow with an attacker-controlled HTTP request body, potentially triggering downstream side effects such as API calls, database writes, or deployments.

The application does not adequately verify the identity of a user, device, or process before granting access. Typical impact: unauthorized access to functions or data reserved for authenticated parties.

GHSA-9R75-G2CR-3H76 has a CVSS score of 5.3 (Medium). The vector is network-reachable, no 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 (4.2.0-beta.64); upgrading removes the vulnerable code path.

Kodem intelligence

• Upgrade to version 4.2.0-beta.64. The fix removes the token option from createWebhook() so that webhook tokens are always randomly generated by the SDK.
• Runs created with versions prior to 4.2.0-beta.64, that are 1) still active (i.e. running), and 2) have open hooks, are still susceptible to this vulnerability. If users suspect the hook tokens are predictable or leaked - consider cancelling those runs and restarting them on the latest patch.

1. What is GHSA-9R75-G2CR-3H76? GHSA-9R75-G2CR-3H76 is a medium-severity improper authentication vulnerability in workflow (npm), affecting versions <= 4.1.0-beta.63. It is fixed in 4.2.0-beta.64. The application does not adequately verify the identity of a user, device, or process before granting access.
2. How severe is GHSA-9R75-G2CR-3H76? GHSA-9R75-G2CR-3H76 has a CVSS score of 5.3 (Medium). 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 packages are affected by GHSA-9R75-G2CR-3H76?
   • workflow (npm) (versions <= 4.1.0-beta.63)
   • @workflow/core (npm) (versions <= 4.1.0-beta.63)
4. Is there a fix for GHSA-9R75-G2CR-3H76? Yes. GHSA-9R75-G2CR-3H76 is fixed in 4.2.0-beta.64. Upgrade to this version or later.
5. Is GHSA-9R75-G2CR-3H76 exploitable, and should I be worried? Whether GHSA-9R75-G2CR-3H76 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 GHSA-9R75-G2CR-3H76 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 GHSA-9R75-G2CR-3H76?
   • Upgrade workflow to 4.2.0-beta.64 or later
   • Upgrade @workflow/core to 4.2.0-beta.64 or later