Waku: Cross-Origin CSRF on RSC Server Action Dispatch

Exploitation

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

CVSS

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

EPSS

• CVE-2026-49455: 0.17% estimated exploitation activity in the next 30 days; percentile 6.85 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Summary Waku's RSC request dispatcher invokes server actions without validating the request's Origin (or Sec-Fetch-Site) header. A cross-origin web attacker can therefore cause a victim browser to issue an authenticated POST to a registered server action endpoint using a CORS-safelisted content type (text/plain), which does not trigger a preflight. Any state-mutating server action that the application exposes via 'use server' can be invoked with the victim's cookies attached. A working proof-of-concept demonstrates the vulnerability against waku 1.0.0-beta.0 dev server: a cross-origin POST with Content-Type: text/plain invokes a registered 'use server' action and returns HTTP 200 with an RSC stream response. The same defect affects the progressive-enhancement (no-JavaScript) server action path: a cross-origin HTML form auto-submitting multipart/form-data reaches the dispatch through a second unguarded branch of the request handler, dynamically confirmed on 2026-05-17. Both branches…

Published by the source

8 Jul 2026, 20:27 UTC

Last modified by the source

8 Jul 2026, 20:56 UTC

Source last checked

26 Oct 2026, 12:56 UTC

1. Revision 2 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-75w3-gmqx-993q

2. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-75w3-gmqx-993q

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# Patch Next advisory brief: CVE-2026-49455

Advisory: Waku: Cross-Origin CSRF on RSC Server Action Dispatch
IDs: CVE-2026-49455, GHSA-75w3-gmqx-993q
Record: https://patchnext.com/advisories/cve-2026-49455 (revision 2, source checked 26 Oct 2026, 12:56 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 6.5)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: waku 1.0.0-beta.1. A vendor fix does not mean a deployment is fixed.

## Affected components
- npm waku: affected <= 1.0.0-beta.0; fixed in 1.0.0-beta.1

## Suggested inspection (read-only)
- `npm ls waku --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 waku.
- 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-75w3-gmqx-993q (OSV record GHSA-75w3-gmqx-993q lists affected ranges: npm waku >=0 <1.0.0-beta.1 (fixed))
- Verified: https://github.com/advisories/GHSA-75w3-gmqx-993q (GitHub-reviewed advisory GHSA-75w3-gmqx-993q lists affected ranges: npm waku >=0 <=1.0.0-beta.0)

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