5.3

CVSS Score

3.1

-

CVSS Score

Basic Information

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GHSA-9r75-g2cr-3h76

GHSA-9r75-g2cr-3h76: Vercel Workflow Allows Webhook Creation with Predictable User-Specified Tokens

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.

Impact

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.

Fix

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.

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.

(GitHub Advisory)

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GHSA-9r75-g2cr-3h76

GHSA-9r75-g2cr-3h76:

5.3

CVSS Score

3.1

-

CVSS Score

Basic Information

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Technical Details

Package Name	Ecosystem	Vulnerable Versions	First Patched Version
workflow	npm	<= 4.1.0-beta.63	4.2.0-beta.64
@workflow/core	npm	<= 4.1.0-beta.63	4.2.0-beta.64

Technical Details

Vulnerability Intelligence
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Root Cause Analysis

The analysis of the security advisory and the associated commit 30e24d441e735635ffa4522198e6905d0e51e175 clearly points to the createWebhook function as the source of the vulnerability. The core issue was that this function allowed developers to set a predictable token for a publicly accessible webhook endpoint. The patch directly addresses this by modifying the createWebhook function in packages/core/src/workflow/create-hook.ts to explicitly throw an error if the token option is used. Furthermore, the WebhookOptions interface in packages/core/src/create-hook.ts was updated to omit the token property, enforcing this change at the type level. The documentation and example files were also updated to remove the vulnerable usage pattern, confirming that setting a custom token was an intended, but flawed, feature. Therefore, any runtime profile of a vulnerable application would show calls to createWebhook with a token parameter being the entry point for this vulnerability.

Vulnerable functions

createWebhook

packages/core/src/workflow/create-hook.ts

The `createWebhook` function was vulnerable because it accepted a user-provided `token` in its options. The documentation encouraged using predictable, deterministic tokens. This allowed an unauthenticated attacker to guess the token and send arbitrary data to the public webhook endpoint (`/.well-known/workflow/v1/webhook/{token}`), which would then be processed by the associated workflow. The patch mitigates this by removing the `token` option entirely, ensuring that all webhook tokens are randomly generated and non-guessable.

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WAF Rule

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Reasoning

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