# CVE-2026-118666: GraphQL Tools: Shared legacy executor routes one subscription's results to a different caller

Status: published. Published: 2026-10-28. Updated: 2026-11-02.

GraphQL Tools provides utilities for building, stitching, and mocking GraphQL schemas. Prior to version 1.1.36 of the GraphQL Tools legacy WebSocket executor package, buildWSLegacyExecutor in packages/executors/legacy-ws/src/index.ts reuses one WebSocket and replaces its single websocket.onmessage handler whenever a new overlapping subscription starts. The handler delivers LEGACY_WS.DATA frames to the newest observer without comparing data.id with the subscription operation id, so a caller using the same executor can receive another user's authorized subscription payload while the earlier caller's stream is starved. This issue is fixed in version 1.1.36 of the GraphQL Tools legacy WebSocket executor package.

## Remediation

- fix: @graphql-tools/executor-legacy-ws (npm): OSV reports a fixed version 1.1.36. Check the advisory for supported release branches. (source: OSV GHSA-mp66-8ww2-pcwm) — https://github.com/advisories/GHSA-mp66-8ww2-pcwm

## Affected products and versions

- ardatan / graphql-tools: < 9.0.36 (affected). Source: CNA: GitHub_M
- @graphql-tools / executor-legacy-ws: < 1.1.36 (affected). Source: CNA: GitHub_M
-  / @graphql-tools/executor-legacy-ws (@graphql-tools/executor-legacy-ws): ≥ 0; < 1.1.36 (affected, semver); OSV events: introduced 0; fixed 1.1.36. Source: OSV GHSA-mp66-8ww2-pcwm

## Severity and prioritization

- CVSS 4.0: 6 (medium); 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; source: CNA: GitHub_M

- CISA KEV: No listing in collected sources

- EPSS: 0.34% as of 2026-11-02; percentile 26.90%

- SSVC: exploitation poc; automatable yes; technical impact partial; source ADP: CISA-ADP

- Weaknesses: CWE-200

## Exploit evidence

- exploit: https://github.com/ardatan/graphql-tools/security/advisories/GHSA-mp66-8ww2-pcwm (ADP: CISA-ADP)

## References

- https://github.com/ardatan/graphql-tools/security/advisories/GHSA-mp66-8ww2-pcwm (CNA: GitHub_M; x_refsource_CONFIRM)

- https://github.com/ardatan/graphql-tools/pull/8480 (CNA: GitHub_M; x_refsource_MISC)

- https://github.com/ardatan/graphql-tools/commit/c2f226e6f68236be9e4a577f29faeaa92547458b (CNA: GitHub_M; x_refsource_MISC)

- https://github.com/ardatan/graphql-tools/releases/tag/@graphql-tools/executor-legacy-ws@1.1.36 (CNA: GitHub_M; x_refsource_MISC)

- https://github.com/ardatan/graphql-tools/security/advisories/GHSA-mp66-8ww2-pcwm (ADP: CISA-ADP; exploit)

- https://github.com/advisories/GHSA-mp66-8ww2-pcwm (OSV / GitHub Security Advisories; advisory)

- https://osv.dev/vulnerability/GHSA-mp66-8ww2-pcwm (OSV / GitHub Security Advisories; osv)

## Provenance

- CNA: GitHub_M: https://www.cve.org/CVERecord?id=CVE-2026-118666; retrieved 2026-11-03; source updated 2026-11-02

- OSV / GitHub Security Advisories: https://osv.dev/vulnerability/GHSA-mp66-8ww2-pcwm; retrieved 2026-11-03; source updated 2026-10-28

- FIRST EPSS: https://api.first.org/data/v1/epss?cve=CVE-2026-118666; retrieved 2026-11-03; source updated Not reported

Revision: 260a2aec449ac62d18b28efb9c40c079e76f6dc4e66c131d0346a039b32418ef

Canonical: https://y2.dev/cve/CVE-2026-118666

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