GraphQL Tools: Shared legacy executor routes one subscription's results to a different caller

Exploitation

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

CVSS 4.0

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

EPSS

• CVE-2026-118666: 0.34% estimated exploitation activity in the next 30 days; percentile 26.94 (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.

Cross-tenant subscription data leak in `@graphql-tools/executor-legacy-ws`: a shared `websocket.onmessage` is replaced on every `subscribe()`, and `DATA` frames are delivered without checking the protocol operation id

Report metadata | Field | Value | | --- | --- | | Package | `@graphql-tools/executor-legacy-ws` (npm, `pkg:npm/%40graphql-tools/executor-legacy-ws`) | | Repository | https://github.com/ardatan/graphql-tools | | Component | `buildWSLegacyExecutor` → the returned executor's `subscribe(observer)` / `websocket.onmessage` handler | | Vulnerability class | Cross-tenant data leak (subscription results delivered to the wrong caller) | | Verified against | Source at `b5d1c36ebb8ed3868260ffee5bbcbb423ad5c1f1` (package version 1.1.33); published npm tarball `1.1.33` with matching source at `d304214db06e8a4ce9cb41138f199e3bc6ed36f2`; the same behaviour also reproduces on the current release `1.1.35` | | API surface | Public documented API (`buildWSLegacyExecutor`) | | Affected…

Published by the source

28 Oct 2026, 21:05 UTC

Last modified by the source

28 Oct 2026, 21:15 UTC

Source last checked

29 Oct 2026, 06:00 UTC

1. Revision 2 · amended · 29 Oct 2026

   Amended from osv record GHSA-mp66-8ww2-pcwm

2. Revision 1 · created · 28 Oct 2026

   Published from ghsa record GHSA-mp66-8ww2-pcwm

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

# Patch Next advisory brief: CVE-2026-118666

Advisory: GraphQL Tools: Shared legacy executor routes one subscription's results to a different caller
IDs: CVE-2026-118666, GHSA-mp66-8ww2-pcwm
Record: https://patchnext.com/advisories/cve-2026-118666 (revision 2, source checked 29 Oct 2026, 06:00 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 6.0)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: @graphql-tools/executor-legacy-ws 1.1.36. A vendor fix does not mean a deployment is fixed.

## Affected components
- npm @graphql-tools/executor-legacy-ws: affected < 1.1.36; fixed in 1.1.36

## Suggested inspection (read-only)
- `npm ls @graphql-tools/executor-legacy-ws --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 @graphql-tools/executor-legacy-ws.
- 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://github.com/advisories/GHSA-mp66-8ww2-pcwm (GitHub-reviewed advisory GHSA-mp66-8ww2-pcwm lists affected ranges: npm @graphql-tools/executor-legacy-ws >=0 <=1.1.35)
- Verified: https://osv.dev/vulnerability/GHSA-mp66-8ww2-pcwm (OSV record GHSA-mp66-8ww2-pcwm lists affected ranges: npm @graphql-tools/executor-legacy-ws >=0 <1.1.36 (fixed))

Commands are suggestions: review each one before running it.