Flowise: Hardcoded CORS wildcard on TTS endpoint enables cross-origin credential abuse from any webpage

Exploitation

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

CVSS 4.0

6.9 · CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N · score source

EPSS

• CVE-2026-56277: 0.18% estimated exploitation activity in the next 30 days; percentile 7.54 (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 The TTS generation endpoint sets Access-Control-Allow-Origin: as a hardcoded response header, independent of the server's CORS configuration. This enables any webpage to make cross-origin requests to generate speech using stored credentials. Root Cause Impact - Cross-origin credential abuse — any webpage can trigger TTS using stored credentials - Bypasses the server's CORS policy (getCorsOptions()) which is otherwise restrictive by default - Combined with Finding 3 (TTS credential abuse), enables drive-by credential abuse via malicious webpages Suggested Fix Remove the hardcoded CORS wildcard and let the server's CORS middleware handle the headers: --- References - packages/server/src/controllers/text-to-speech/index.ts line 83

Published by the source

20 May 2026, 15:38 UTC

Last modified by the source

8 Jul 2026, 08:27 UTC

Source last checked

26 Oct 2026, 12:52 UTC

1. Revision 3 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-m837-xvxr-vqwg

2. Revision 2 · amended · 24 Oct 2026

   Reviewed OSV alias/range/CVSS4 correction; package source scopes and original publication preserved. No customer finding resolved.

3. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-m837-xvxr-vqwg

Preview the exact text before you copy it. Commands are read-only suggestions; review them before running anything.

# Patch Next advisory brief: CVE-2026-56277

Advisory: Flowise: Hardcoded CORS wildcard on TTS endpoint enables cross-origin credential abuse from any webpage
IDs: CVE-2026-56277, GHSA-m837-xvxr-vqwg
Record: https://patchnext.com/advisories/cve-2026-56277 (revision 3, source checked 26 Oct 2026, 12:52 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 6.9)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: flowise 3.1.2. A vendor fix does not mean a deployment is fixed.

## Affected components
- npm flowise: affected <= 3.1.1; fixed in 3.1.2

## Suggested inspection (read-only)
- `npm ls flowise --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 flowise.
- 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-m837-xvxr-vqwg (OSV record GHSA-m837-xvxr-vqwg lists affected ranges: npm flowise >=0 <3.1.2 (fixed))
- Verified: https://github.com/advisories/GHSA-m837-xvxr-vqwg (GitHub-reviewed advisory GHSA-m837-xvxr-vqwg lists affected ranges: npm flowise >=0 <=3.1.1)

Commands are suggestions: review each one before running it.