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GHSA-9r75-g2cr-3h76

MediumCVSS 5.3 / 10
Published Mar 6, 2026·Last modified Mar 6, 2026
Affected Components(0)

No affected components available

Description

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.
Risk Scores
Base Score
5.3

The vulnerability can be exploited over the network without needing physical access. It is easy for an attacker to exploit this vulnerability. An attacker does not need any special privileges or access rights. No user interaction is needed for the attacker to exploit this vulnerability. The impact is confined to the system where the vulnerability exists. There is a low impact on the integrity of the data.

Threat Intelligence
4.9

Exploitation attempts have been detected. Elevated vigilance and prompt remediation are advised.

EPSS
N/A

Probability that this vulnerability will be exploited in the wild within the next 30 days.

Exploit
Not available

We did not find any exploit available. Neither in GitHub repositories nor in the Exploit-Database.

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Medium severity
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