Vercel Workflow Allows Webhook Creation with Predictable User-Specified Tokens

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

5.3 · CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N

EPSS

No dated EPSS signal available.

As published by the source; long descriptions are shortened.

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…

Published by the source

6 Mar 2026, 18:45 UTC

Last modified by the source

6 Mar 2026, 19:02 UTC

Source last checked

26 Oct 2026, 12:43 UTC

1. Revision 2 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-9r75-g2cr-3h76

2. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-9r75-g2cr-3h76

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# Patch Next advisory brief: GHSA-9r75-g2cr-3h76

Advisory: Vercel Workflow Allows Webhook Creation with Predictable User-Specified Tokens
IDs: GHSA-9r75-g2cr-3h76
Record: https://patchnext.com/advisories/ghsa-9r75-g2cr-3h76 (revision 2, source checked 26 Oct 2026, 12:43 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 5.3)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: workflow 4.2.0-beta.64; @workflow/core 4.2.0-beta.64. A vendor fix does not mean a deployment is fixed.

## Affected components
- npm workflow: affected <= 4.1.0-beta.63; fixed in 4.2.0-beta.64
- npm @workflow/core: affected <= 4.1.0-beta.63; fixed in 4.2.0-beta.64

## Suggested inspection (read-only)
- `npm ls workflow --all`: lists every installed copy and version, including transitive ones. Run in the project root after `npm ci`.
- `npm ls @workflow/core --all`: lists every installed copy and version, including transitive ones. Run in the project root after `npm ci`.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on workflow, @workflow/core.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GHSA-9r75-g2cr-3h76 (OSV record GHSA-9r75-g2cr-3h76 lists affected ranges: npm workflow >=0 =0 <4.2.0-beta.64 (fixed))
- Verified: https://github.com/advisories/GHSA-9r75-g2cr-3h76 (GitHub-reviewed advisory GHSA-9r75-g2cr-3h76 lists affected ranges: npm workflow >=0 =0 <=4.1.0-beta.63)

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